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115-616: The Nile monitor ( Varanus niloticus ) is a large member of the monitor family ( Varanidae ) found throughout most of Sub-Saharan Africa , particularly in drier regions, and along the Nile River and its tributaries in East Africa . Additionally, there are modern, invasive populations in North America . The population found in West African forests and savannahs is sometimes recognized as
230-429: A helical structure (i.e., shaped like a corkscrew). Their double-helix model had two strands of DNA with the nucleotides pointing inward, each matching a complementary nucleotide on the other strand to form what look like rungs on a twisted ladder. This structure showed that genetic information exists in the sequence of nucleotides on each strand of DNA. The structure also suggested a simple method for replication : if
345-534: A sexual process for transferring DNA from one cell to another cell (usually of the same species). Transformation requires the action of numerous bacterial gene products , and its primary adaptive function appears to be repair of DNA damages in the recipient cell. The diploid nature of chromosomes allows for genes on different chromosomes to assort independently or be separated from their homologous pair during sexual reproduction wherein haploid gametes are formed. In this way new combinations of genes can occur in
460-573: A DNA molecule. In 1983, Kary Banks Mullis developed the polymerase chain reaction , providing a quick way to isolate and amplify a specific section of DNA from a mixture. The efforts of the Human Genome Project , Department of Energy, NIH, and parallel private efforts by Celera Genomics led to the sequencing of the human genome in 2003. At its most fundamental level, inheritance in organisms occurs by passing discrete heritable units, called genes , from parents to offspring. This property
575-486: A complex trait is called heritability . Measurement of the heritability of a trait is relative—in a more variable environment, the environment has a bigger influence on the total variation of the trait. For example, human height is a trait with complex causes. It has a heritability of 89% in the United States. In Nigeria, however, where people experience a more variable access to good nutrition and health care , height has
690-483: A different parent. Many species have so-called sex chromosomes that determine the sex of each organism. In humans and many other animals, the Y chromosome contains the gene that triggers the development of the specifically male characteristics. In evolution, this chromosome has lost most of its content and also most of its genes, while the X chromosome is similar to the other chromosomes and contains many genes. This being said, Mary Frances Lyon discovered that there
805-546: A diploid cell with paired chromosomes. Diploid organisms form haploids by dividing, without replicating their DNA, to create daughter cells that randomly inherit one of each pair of chromosomes. Most animals and many plants are diploid for most of their lifespan, with the haploid form reduced to single cell gametes such as sperm or eggs . Although they do not use the haploid/diploid method of sexual reproduction, bacteria have many methods of acquiring new genetic information. Some bacteria can undergo conjugation , transferring
920-517: A few species also eat fruit and vegetation . The generic name Varanus is derived from the Arabic word ورل waral [Standard Arabic] / ورر warar [colloquially] / ورن waran [colloquially], from a common Semitic root ouran , waran , warar or waral , meaning "lizard beast". In English, they are known as "monitors" or "monitor lizards". The earlier term "monitory lizard" became rare by about 1920. The name may have been suggested by
1035-429: A gene is used to produce a specific amino acid sequence . This process begins with the production of an RNA molecule with a sequence matching the gene's DNA sequence, a process called transcription . This messenger RNA molecule then serves to produce a corresponding amino acid sequence through a process called translation . Each group of three nucleotides in the sequence, called a codon , corresponds either to one of
1150-482: A heritability of only 62%. The molecular basis for genes is deoxyribonucleic acid (DNA). DNA is composed of deoxyribose (sugar molecule), a phosphate group, and a base (amine group). There are four types of bases: adenine (A), cytosine (C), guanine (G), and thymine (T). The phosphates make phosphodiester bonds with the sugars to make long phosphate-sugar backbones. Bases specifically pair together (T&A, C&G) between two backbones and make like rungs on
1265-455: A high aerobic scope that is afforded, in part, by their heart anatomy. Whereas most reptiles are considered to have three-chambered hearts, the hearts of monitor lizards – as with those of boas and pythons – have a well developed ventricular septum that completely separates the pulmonary and systemic sides of the circulatory system during systole . This allows monitor lizards to create mammalian-equivalent pressure differentials between
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#17328586122831380-435: A higher body temperature. In a low-temperature environment, however, the protein's structure is stable and produces dark-hair pigment normally. The protein remains functional in areas of skin that are colder—such as its legs, ears, tail, and face—so the cat has dark hair at its extremities. Environment plays a major role in effects of the human genetic disease phenylketonuria . The mutation that causes phenylketonuria disrupts
1495-503: A ladder. The bases, phosphates, and sugars together make a nucleotide that connects to make long chains of DNA. Genetic information exists in the sequence of these nucleotides, and genes exist as stretches of sequence along the DNA chain. These chains coil into a double a-helix structure and wrap around proteins called Histones which provide the structural support. DNA wrapped around these histones are called chromosomes. Viruses sometimes use
1610-507: A large cage as juveniles quickly grow when fed a varied diet, and large adults often require custom-built quarters. "There are few lizards less suited to life in captivity than the Nile monitor. Buffrenil (1992) considered that, when fighting for its life, a Nile monitor was a more dangerous adversary than a crocodile of a similar size. Their care presents particular problems on account of the lizards' enormous size and lively dispositions. Very few of
1725-505: A living cell or organism may increase or decrease gene transcription. A classic example is two seeds of genetically identical corn, one placed in a temperate climate and one in an arid climate (lacking sufficient waterfall or rain). While the average height the two corn stalks could grow to is genetically determined, the one in the arid climate only grows to half the height of the one in the temperate climate due to lack of water and nutrients in its environment. The word genetics stems from
1840-456: A phenotype involves studying identical and fraternal twins , or other siblings of multiple births . Identical siblings are genetically the same since they come from the same zygote. Meanwhile, fraternal twins are as genetically different from one another as normal siblings. By comparing how often a certain disorder occurs in a pair of identical twins to how often it occurs in a pair of fraternal twins, scientists can determine whether that disorder
1955-1128: A separate species, the West African Nile monitor ( V. stellatus ). While it is dwarfed by its larger relatives, such as the Komodo dragon , the Asian water monitor or the crocodile monitor , it is still one of the largest lizards in the world , reaching (and even surpassing) Australia’s perentie in size. Other common names include the African small-grain lizard , as well as iguana and various forms derived from it, such as guana , water leguaan or river leguaan (leguan, leguaan, and likkewaan mean monitor lizard in South African English , and can be used interchangeably). A feral population of Nile monitors (descended from escaped or intentionally-released pets) has become established in several locations in South Florida . In addition to any illegally-released animals, it
2070-524: A separate species: the West African Nile monitor ( V. stellatus ). It is estimated to have split from the others in the Nile monitor complex about 7.7 million years ago, making it older than the split between humans and chimpanzees . In contrast, those in the Central African rainforests are genetically similar to the Nile monitor. This essentially splits the ornate monitor—as defined in 1997—into two:
2185-403: A series of genes can be combined to form a linear linkage map that roughly describes the arrangement of the genes along the chromosome. Genes express their functional effect through the production of proteins, which are molecules responsible for most functions in the cell. Proteins are made up of one or more polypeptide chains, each composed of a sequence of amino acids . The DNA sequence of
2300-457: A single parent. Offspring that are genetically identical to their parents are called clones . Eukaryotic organisms often use sexual reproduction to generate offspring that contain a mixture of genetic material inherited from two different parents. The process of sexual reproduction alternates between forms that contain single copies of the genome ( haploid ) and double copies ( diploid ). Haploid cells fuse and combine genetic material to create
2415-808: A sizeable number of Nile monitor sightings include Palm Beach County just southwest of West Palm Beach along State Road 80 . In July 2008, a Nile monitor was spotted in Homestead , a small city southwest of Miami . Other sightings have been reported near Hollywood , Naranja , and as far south as Key Largo in the Florida Keys. The potential for the established population of Nile monitors in Lee, Charlotte, and other counties in Florida, to negatively impact indigenous crocodilians, such as American alligators ( Alligator mississippiensis ), and American crocodiles ( Crocodylus acutus ),
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#17328586122832530-448: A small circular piece of DNA to another bacterium. Bacteria can also take up raw DNA fragments found in the environment and integrate them into their genomes, a phenomenon known as transformation . These processes result in horizontal gene transfer , transmitting fragments of genetic information between organisms that would be otherwise unrelated. Natural bacterial transformation occurs in many bacterial species, and can be regarded as
2645-400: A smooth blend of traits from their parents. Mendel's work provided examples where traits were definitely not blended after hybridization, showing that traits are produced by combinations of distinct genes rather than a continuous blend. Blending of traits in the progeny is now explained by the action of multiple genes with quantitative effects . Another theory that had some support at that time
2760-596: A staple in the reptile pet trade. The most commonly kept monitors are the savannah monitor and Ackie dwarf monitor , due to their relatively small size, low cost, and relatively calm dispositions with regular handling. Among others, black-throated , Timor , Asian water , Nile , mangrove , emerald tree , black tree , roughneck , Dumeril's , peach-throated , crocodile , and Argus monitors have been kept in captivity. Monitor lizards are poached in some South- and Southeast Asian countries, as their organs and fat are used in some traditional medicines , although there
2875-448: A transition of heredity from its status as myth to that of a scientific discipline, by providing a fundamental theoretical basis for genetics in the twentieth century. Other theories of inheritance preceded Mendel's work. A popular theory during the 19th century, and implied by Charles Darwin 's 1859 On the Origin of Species , was blending inheritance : the idea that individuals inherit
2990-412: A unique three-dimensional structure for that protein, and the three-dimensional structures of proteins are related to their functions. Some are simple structural molecules, like the fibers formed by the protein collagen . Proteins can bind to other proteins and simple molecules, sometimes acting as enzymes by facilitating chemical reactions within the bound molecules (without changing the structure of
3105-400: A variety of hereditary characteristics that replicate and remain active throughout generations. While haploid organisms have only one copy of each chromosome, most animals and many plants are diploid , containing two of each chromosome and thus two copies of every gene. The two alleles for a gene are located on identical loci of the two homologous chromosomes , each allele inherited from
3220-639: A wide variety of prey items, including fish, frogs and toads (even poisonous ones of the genera Breviceps and Sclerophrys ), small reptiles (such as turtles , snakes , lizards , and young crocodiles ), birds, rodents, other small mammals (up to domestic cats and young antelopes [ Raphicerus ]), eggs (including those of crocodiles, agamids, other monitor lizards, and birds), invertebrates (such as beetles , termites , orthopterans , crabs , caterpillars , spiders , millipedes , earthworms , snails , and slugs ), carrion , human wastes, and feces. Nile monitors are native to Sub-Saharan Africa and along
3335-648: Is Archaeovaranus from the Eocene of China, suggesting that the genus Varanus is of Asian origin. The oldest fossils of Varanus date to the early Miocene . Many of the species within the various subgenera also form species complexes with each other: Euprepriosaurus Odatria Varanus Polydaedalus Empagusia Soterosaurus The tree monitors of the V. prasinus species complex ( V. prasinus , V. beccarii , V. boehmei , V. bogerti , V. keithhornei , V. kordensis , V. macraei , V. reisingeri , V. telenesetes ) were once in
3450-488: Is X-chromosome inactivation during reproduction to avoid passing on twice as many genes to the offspring. Lyon's discovery led to the discovery of X-linked diseases. When cells divide, their full genome is copied and each daughter cell inherits one copy. This process, called mitosis , is the simplest form of reproduction and is the basis for asexual reproduction. Asexual reproduction can also occur in multicellular organisms, producing offspring that inherit their genome from
3565-425: Is a somewhat ambiguous definition of what is referred to as a gene. Trait inheritance and molecular inheritance mechanisms of genes are still primary principles of genetics in the 21st century, but modern genetics has expanded to study the function and behavior of genes. Gene structure and function, variation, and distribution are studied within the context of the cell , the organism (e.g. dominance ), and within
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3680-734: Is also found in the Americas as an invasive species . About 80 species are recognized. Monitor lizards have long necks, powerful tails and claws, and well-developed limbs. The adult length of extant species ranges from 20 cm (7.9 in) in some species such as Varanus sparnus , to over 3 m (10 ft) in the case of the Komodo dragon , though the extinct megalania ( Varanus priscus ) may have reached lengths of more than 7 m (23 ft). Most monitor species are terrestrial , but many are also arboreal or semiaquatic. While most monitor lizards are carnivorous , eating smaller reptiles, fish , birds , insects , small mammals, and eggs,
3795-639: Is banned under the Protected Species Act. Varanus is the only living genus of the family Varanidae . Varanids last shared a common ancestor with their closest living relatives, earless "monitors" , during the Late Cretaceous . The oldest known varanids are from the Late Cretaceous of Mongolia. During the Eocene , the varanid Saniwa occurred in North America. The closest known relative of Varanus
3910-478: Is caused by genetic or postnatal environmental factors. One famous example involved the study of the Genain quadruplets , who were identical quadruplets all diagnosed with schizophrenia . The genome of a given organism contains thousands of genes, but not all these genes need to be active at any given moment. A gene is expressed when it is being transcribed into mRNA and there exist many cellular methods of controlling
4025-563: Is diverse and complex, as a result of the diverse ecological niches monitor lizards occupy. For example, many species have anticoagulant venom, disrupting clotting through a combination of fibrinogenolysis and blocking platelet aggregation. Amongst them, arboreal species, such as the tree monitors and the banded monitor , have by far the strongest fibrinogenolytic venom. As a result, wounds from monitor lizard bites often bleed more than they would if they were simply lacerations. Venom may also cause hypotension . In some species such as
4140-615: Is enormous, given that they normally raid crocodile nests, eat eggs, and prey on small crocodiles in Africa. Anecdotal evidence indicates a high rate of disappearance of domestic pets and feral cats in Cape Coral. Nile monitors are often found in the pet trade despite their highly aggressive demeanor and resistance to taming. Juvenile monitors will tail whip as a defensive measure, and as adults, they are capable of inflicting moderate to serious wounds from biting and scratching. Nile monitors require
4255-528: Is known by several names in Yoruba , including awọ́nríwọ́n , awọ̀n , and àlégbà . In Wolof it is known as mbossé or bar , and is the traditional totem of the city of Kaolack . Due to confusion with the large New World lizards of the family Iguanidae , the lizards became known as " goannas " in Australia. Similarly, in South African English , they are referred to as leguaans , or likkewaans , from
4370-483: Is no scientific evidence as to their effectiveness. Monitor lizard meat, particularly the tongue and liver, is eaten in parts of India and Malaysia and is supposed to be an aphrodisiac . In parts of Pakistan and southern India, as well in Northeastern India, particularly Assam, the different parts of monitor lizards are traditionally used for treating rheumatic pain, skin infections and hemorrhoids , and
4485-441: Is responsible for the development of structures within multicellular organisms, these patterns arise from the complex interactions between many cells. Within eukaryotes , there exist structural features of chromatin that influence the transcription of genes, often in the form of modifications to DNA and chromatin that are stably inherited by daughter cells. These features are called " epigenetic " because they exist "on top" of
4600-655: Is speculated that during particularly intense hurricane seasons in Florida, many reptiles potentially escape when their enclosures are damaged or inadvertently unlocked; as Florida has a semi-tropical to tropical climate, many reptiles are housed outdoors, and poorly-secured enclosures may become damaged during bad storms. Along with Nile monitors, Florida is infamous for its feral populations of agamas , Argentine black and white tegus , Burmese pythons , green iguanas , Madagascar giant day geckos , and panther and veiled chameleons , among others. Many of these species are thought to be descendants of hurricane escapees. Members of
4715-497: Is the physical basis for inheritance: DNA replication duplicates the genetic information by splitting the strands and using each strand as a template for synthesis of a new partner strand. Genes are arranged linearly along long chains of DNA base-pair sequences. In bacteria , each cell usually contains a single circular genophore , while eukaryotic organisms (such as plants and animals) have their DNA arranged in multiple linear chromosomes. These DNA strands are often extremely long;
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4830-694: Is the same as that which Mendel published. In his third law, he developed the basic principles of mutation (he can be considered a forerunner of Hugo de Vries ). Festetics argued that changes observed in the generation of farm animals, plants, and humans are the result of scientific laws. Festetics empirically deduced that organisms inherit their characteristics, not acquire them. He recognized recessive traits and inherent variation by postulating that traits of past generations could reappear later, and organisms could produce progeny with different attributes. These observations represent an important prelude to Mendel's theory of particulate inheritance insofar as it features
4945-597: Is the study of genes , genetic variation , and heredity in organisms . It is an important branch in biology because heredity is vital to organisms' evolution . Gregor Mendel , a Moravian Augustinian friar working in the 19th century in Brno , was the first to study genetics scientifically. Mendel studied "trait inheritance", patterns in the way traits are handed down from parents to offspring over time. He observed that organisms (pea plants) inherit traits by way of discrete "units of inheritance". This term, still used today,
5060-544: Is used for membranes in traditional drums (called kundu ), and these lizards are referred to as kundu palai or "drum lizard" in Tok Pisin , the main Papuan trade language. Monitor lizard skins are prized in making the resonant part of serjas (Bodo folk sarangis) and dotaras (native strummed string instruments of Assam, Bengal and other eastern states). The leather is also used in making a Carnatic music percussion instrument called
5175-583: The kanjira . The meat of monitor lizards is eaten by some tribes in India, Nepal, the Philippines, Australia, South Africa and West Africa as a supplemental meat source. Both meat and eggs are also eaten in Southeast Asian countries such as Vietnam and Thailand as a delicacy. According to IUCN Red List of threatened species, most of the monitor lizards species fall in the categories of least concern, but
5290-479: The Blue-eyed Mary ( Omphalodes verna ), for example, there exists a gene with alleles that determine the color of flowers: blue or magenta. Another gene, however, controls whether the flowers have color at all or are white. When a plant has two copies of this white allele, its flowers are white—regardless of whether the first gene has blue or magenta alleles. This interaction between genes is called epistasis , with
5405-1688: The Caroline Islands ); batua or butaan ( Luzon ); alu ( Bali ); hora or ghora ( Komodo group of islands); phut ( Burmese ); and guibang ( Manobo ). In South Asia , they are known as hangkok in Meitei , mwpou in Boro, ghorpad घोरपड in Marathi , uḍumbu உடும்பு in Tamil and udumbu ഉടുമ്പ് in Malayalam , bilgoh in Bhojpuri , gohi (गोहि) in Maithili , in Sinhala as තලගොයා / කබරගොයා ( talagoya [land monitor] / kabaragoya [water monitor where kabara means vitiligo] ), in Telugu as uḍumu (ఉడుము), in Kannada as uḍa (ಉಡ), in Punjabi and Magahi as गोह ( goh ), in Assamese as gui xaap , in Odia as ଗୋଧି ( godhi ), and in Bengali as গোসাপ ( goshaap ) or গুইসাপ ( guishaap ), and गोह ( goh ) in Hindi and गोधा ( godhā ) in Sanskrit . The West African Nile monitor
5520-824: The Dutch term for the Iguanidae, leguanen . The various species cover a vast area, occurring through Africa, the Indian subcontinent , to China , the Ryukyu Islands in southern Japan , south to Southeast Asia to Thailand , Malaysia , Brunei , Indonesia , the Philippines , New Guinea , Australia , and islands of the Indian Ocean and the South China Sea . They have also been introduced outside of their natural range, for instance,
5635-682: The German word Waran (borrowed from Arabic) was connected to warnen (to warn), leading him to incorrectly Latinize it as monitor ('warner', 'adviser'). Austronesian languages spoken across Southeast Asia , where varanids are common, have a large number of slightly related local names for them. They are usually known as biawak ( Malay , including Indonesian standard variety), bayawak ( Filipino ), binjawak or minjawak or nyambik ( Javanese ), or variations thereof. Other names include hokai ( Solomon Islands ); bwo , puo , or soa ( Maluku ); halo ( Cebu ); galuf or kaluf ( Micronesia and
5750-506: The Komodo dragon and the desert monitor , venom also induces a powerful neurotoxic effect. In the latter species for instance, envenomation causes immediate paralysis in rodents (but not birds) and lesser effects of the same nature in humans. At least some species of monitors are known to be able to count; studies feeding rock monitors varying numbers of snails showed that they can distinguish numbers up to six. Nile monitors have been observed to cooperate when foraging; one animal lures
5865-758: The Nile . They are not found in any of the desert regions of Africa (notably Sahara , Kalahari and much of the Horn of Africa ), however, they thrive around rivers. Nile monitors were reported to live in and around the Jordan River , Dead Sea , and wadis of the Judaean Desert in Israel until the late 19th century, though they are now extinct in the region. In Florida in the United States, established breeding populations of Nile monitors have been known to exist in different parts of
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#17328586122835980-538: The Sahel ( Mali to Ethiopia ) and Nile regions. Despite the differences, the Reptile Database maintains both the ornate monitor and West African Nile monitor as synonyms of the Nile monitor, but do note that this broad species definition includes distinctive subpopulations. The Nile monitor is Africa's longest lizard. They grow from about 120 to 220 cm (3 ft 11 in to 7 ft 3 in) in length, with
6095-685: The West African Nile monitor is now found in South Florida . Monitor lizards also occurred widely in Europe in the Neogene , with the last known remains in the region dating to the Middle Pleistocene . Most monitor lizards are almost entirely carnivorous, consuming prey as varied as insects, crustaceans , arachnids , myriapods , molluscs , fish, amphibians , reptiles, birds, and mammals. Most species feed on invertebrates as juveniles and shift to feeding on vertebrates as adults. Deer make up about 50% of
6210-413: The ancient Greek γενετικός genetikos meaning "genitive"/"generative", which in turn derives from γένεσις genesis meaning "origin". The observation that living things inherit traits from their parents has been used since prehistoric times to improve crop plants and animals through selective breeding . The modern science of genetics, seeking to understand this process, began with
6325-415: The neutral theory of molecular evolution through publishing the nearly neutral theory of molecular evolution . In this theory, Ohta stressed the importance of natural selection and the environment to the rate at which genetic evolution occurs. One important development was chain-termination DNA sequencing in 1977 by Frederick Sanger . This technology allows scientists to read the nucleotide sequence of
6440-421: The DNA sequence and retain inheritance from one cell generation to the next. Because of epigenetic features, different cell types grown within the same medium can retain very different properties. Although epigenetic features are generally dynamic over the course of development, some, like the phenomenon of paramutation , have multigenerational inheritance and exist as rare exceptions to the general rule of DNA as
6555-624: The F1 offspring mate with each other, the offspring are called the "F2" (second filial) generation. One of the common diagrams used to predict the result of cross-breeding is the Punnett square . When studying human genetic diseases, geneticists often use pedigree charts to represent the inheritance of traits. These charts map the inheritance of a trait in a family tree. Organisms have thousands of genes, and in sexually reproducing organisms these genes generally assort independently of each other. This means that
6670-496: The Greek word genesis —γένεσις, "origin", predates the noun and was first used in a biological sense in 1860. Bateson both acted as a mentor and was aided significantly by the work of other scientists from Newnham College at Cambridge, specifically the work of Becky Saunders , Nora Darwin Barlow , and Muriel Wheldale Onslow . Bateson popularized the usage of the word genetics to describe
6785-530: The Nile monitor species group were already well known to Africans in ancient times. For example, they were commonly caught, likely as food, in the Djenné-Djenno culture at least a millennium ago. The Nile monitor twice was given a scientific name by Carl Linnaeus : First as Lacerta monitor in 1758 in the 10th edition of Systema Naturae , the starting point of zoological nomenclature . He described it again in 1766 as Lacerta nilotica . Despite being older,
6900-511: The Nile monitor ( V. niloticus ); as synonyms or as a valid subspecies . This was the standard treatment until 1997, when a taxonomic review based on color and morphology indicated that the ornate monitor is distinctive and revalidated it as a separate species from rainforests of West and Central Africa . In 2016, a review based primarily on genetics came to another result. They found that monitors from West African forests and adjacent savannah are distinctive and worthy of recognition as
7015-410: The West African Nile monitor and the Nile monitor, with the "ornate" appearing to be more frequent in densely forested habitats. With the West African Nile monitor as a separate species, there are two main clades in the Nile monitor: A widespread clade found throughout much of Southern , Central and East Africa , as well as more locally in coastal West Africa. The other clade includes the monitors of
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#17328586122837130-448: The ability of the body to break down the amino acid phenylalanine , causing a toxic build-up of an intermediate molecule that, in turn, causes severe symptoms of progressive intellectual disability and seizures. However, if someone with the phenylketonuria mutation follows a strict diet that avoids this amino acid, they remain normal and healthy. A common method for determining how genes and environment ("nature and nurture") contribute to
7245-444: The adaptive function of repair of DNA damages. The first cytological demonstration of crossing over was performed by Harriet Creighton and Barbara McClintock in 1931. Their research and experiments on corn provided cytological evidence for the genetic theory that linked genes on paired chromosomes do in fact exchange places from one homolog to the other. The probability of chromosomal crossover occurring between two given points on
7360-440: The basis for inheritance. During the process of DNA replication, errors occasionally occur in the polymerization of the second strand. These errors, called mutations, can affect the phenotype of an organism, especially if they occur within the protein coding sequence of a gene. Error rates are usually very low—1 error in every 10–100 million bases—due to the "proofreading" ability of DNA polymerases . Processes that increase
7475-499: The bulkier rock monitor . They have muscular bodies, strong legs, and powerful jaws. Their teeth are sharp and pointed in juvenile animals and become blunt and peg-like in adults. They also possess sharp claws used for climbing, digging, defense, or tearing at their prey. Like all monitors, they have forked tongues, with highly developed olfactory properties. The Nile monitor has quite striking, but variable, skin patterns, as they are greyish-brown above with greenish-yellow barring on
7590-404: The cat plays the role of the environment. The cat's genes code for dark hair, thus the hair-producing cells in the cat make cellular proteins resulting in dark hair. But these dark hair-producing proteins are sensitive to temperature (i.e. have a mutation causing temperature-sensitivity) and denature in higher-temperature environments, failing to produce dark-hair pigment in areas where the cat has
7705-429: The cell, these genes for tryptophan synthesis are no longer needed. The presence of tryptophan directly affects the activity of the genes—tryptophan molecules bind to the tryptophan repressor (a transcription factor), changing the repressor's structure such that the repressor binds to the genes. The tryptophan repressor blocks the transcription and expression of the genes, thereby creating negative feedback regulation of
7820-421: The chromosome is related to the distance between the points. For an arbitrarily long distance, the probability of crossover is high enough that the inheritance of the genes is effectively uncorrelated. For genes that are closer together, however, the lower probability of crossover means that the genes demonstrate genetic linkage; alleles for the two genes tend to be inherited together. The amounts of linkage between
7935-422: The combined DNA sequences of all chromosomes) is called the genome . DNA is most often found in the nucleus of cells, but Ruth Sager helped in the discovery of nonchromosomal genes found outside of the nucleus. In plants, these are often found in the chloroplasts and in other organisms, in the mitochondria. These nonchromosomal genes can still be passed on by either partner in sexual reproduction and they control
8050-486: The context of a population. Genetics has given rise to a number of subfields, including molecular genetics , epigenetics , and population genetics . Organisms studied within the broad field span the domains of life ( archaea , bacteria , and eukarya ). Genetic processes work in combination with an organism's environment and experiences to influence development and behavior , often referred to as nature versus nurture . The intracellular or extracellular environment of
8165-411: The diet of adult Komodo dragons, the largest monitor species. In contrast, three arboreal species from the Philippines, Varanus bitatawa , mabitang , and olivaceus , are primarily fruit eaters . Monitor lizards are considered unique among animals in that its members are relatively morphologically conservative, yet show a very large size range. However, finer morphological features such as
8280-417: The expression of genes such that proteins are produced only when needed by the cell. Transcription factors are regulatory proteins that bind to DNA, either promoting or inhibiting the transcription of a gene. Within the genome of Escherichia coli bacteria, for example, there exists a series of genes necessary for the synthesis of the amino acid tryptophan . However, when tryptophan is already available to
8395-571: The female crocodile away from her nest, while the other opens the nest to feed on the eggs. The decoy then returns to also feed on the eggs. Komodo dragons at the National Zoo in Washington, DC , recognize their keepers and seem to have distinct personalities. Blue and green tree monitors in British zoos have been observed shredding leaves, apparently as a form of play. Monitor lizards have become
8510-409: The highest standard metabolic rates of all extant reptiles. Like snakes, monitor lizards have highly forked tongues that act as part of the "smell" sense, where the tips of the tongue carry molecules from the environment to sensory organs in the skull. The forked apparatus allows for these lizards to sense boundaries in the molecules they collect, almost smelling in "stereo". Monitor lizards have
8625-464: The information an organism uses to function, the environment plays an important role in determining the ultimate phenotypes an organism displays. The phrase " nature and nurture " refers to this complementary relationship. The phenotype of an organism depends on the interaction of genes and the environment. An interesting example is the coat coloration of the Siamese cat . In this case, the body temperature of
8740-406: The inheritance of an allele for yellow or green pea color is unrelated to the inheritance of alleles for white or purple flowers. This phenomenon, known as " Mendel's second law " or the "law of independent assortment," means that the alleles of different genes get shuffled between parents to form offspring with many different combinations. Different genes often interact to influence the same trait. In
8855-427: The largest human chromosome, for example, is about 247 million base pairs in length. The DNA of a chromosome is associated with structural proteins that organize, compact, and control access to the DNA, forming a material called chromatin ; in eukaryotes, chromatin is usually composed of nucleosomes , segments of DNA wound around cores of histone proteins. The full set of hereditary material in an organism (usually
8970-557: The largest specimens attaining 244 cm (8 ft). In an average-sized specimen, the snout-to-vent length will be around 50 cm (1 ft 8 in). In body mass, adults have been reported to vary widely, one study claiming only 0.8 to 1.7 kg (1.8 to 3.7 lb), others state weights ranging from 5.9 to 15 kg (13 to 33 lb) in big monitors. Variations may be due to age or environmental conditions. Exceptionally large specimens may scale as much as 20 kg (44 lb), but this species weighs somewhat less on average than
9085-651: The name proposed in 1758 is invalid because it was rejected in ICZN opinion 540, making the name of 1766 valid. The genus Varanus was coined in 1820 by Blasius Merrem . Six years later Leopold Fitzinger moved the Nile monitor into this genus as Varanus niloticus , the currently accepted scientific name for the species. As traditionally defined, the Nile monitor is a species complex . The ornate monitor ( V. ornatus ) and West African Nile monitor ( V. stellatus ) were described as species in 1802 and 1803 by François Marie Daudin . In 1942, Robert Mertens moved them both into
9200-557: The nature of inheritance in plants. In his paper " Versuche über Pflanzenhybriden " (" Experiments on Plant Hybridization "), presented in 1865 to the Naturforschender Verein (Society for Research in Nature) in Brno , Mendel traced the inheritance patterns of certain traits in pea plants and described them mathematically. Although this pattern of inheritance could only be observed for a few traits, Mendel's work suggested that heredity
9315-399: The occasional habit of varanids to stand on their two hind legs and to appear to "monitor", or perhaps from their supposed habit of "warning people of the approach of venomous animals". But all of these explanations for the name "monitor" postdate Linnaeus giving the scientific name Lacerta monitor to the Nile monitor in 1758, which may have been based on a mistaken idea by Linnaeus that
9430-500: The offspring of a mating pair. Genes on the same chromosome would theoretically never recombine. However, they do, via the cellular process of chromosomal crossover . During crossover, chromosomes exchange stretches of DNA, effectively shuffling the gene alleles between the chromosomes. This process of chromosomal crossover generally occurs during meiosis , a series of cell divisions that creates haploid cells. Meiotic recombination , particularly in microbial eukaryotes , appears to serve
9545-464: The oil is used as an aphrodisiac lubricant ( sande ka tel ). Consuming raw blood and flesh of monitor lizards has been reported to cause eosinophilic meningoencephalitis , as some monitors are hosts for the parasite Angiostrongylus cantonensis . "Large-scale exploitation" of monitor lizards is undertaken for their skins, which are described as being "of considerable utility" in the leather industry. In Papua New Guinea , monitor lizard leather
9660-435: The original sequence. A particularly important source of DNA damages appears to be reactive oxygen species produced by cellular aerobic respiration , and these can lead to mutations. In organisms that use chromosomal crossover to exchange DNA and recombine genes, errors in alignment during meiosis can also cause mutations. Errors in crossover are especially likely when similar sequences cause partner chromosomes to adopt
9775-465: The people who buy brightly-coloured baby Nile monitors can be aware that, within a couple of years, their purchase will have turned into an enormous, ferocious carnivore, quite capable of breaking the family cat's neck with a single snap and swallowing it whole." Monitor lizard Monitor lizards are lizards in the genus Varanus , the only extant genus in the family Varanidae . They are native to Africa, Asia, and Oceania , and one species
9890-470: The phenotype of the organism, while the other allele is called recessive as its qualities recede and are not observed. Some alleles do not have complete dominance and instead have incomplete dominance by expressing an intermediate phenotype, or codominance by expressing both alleles at once. When a pair of organisms reproduce sexually , their offspring randomly inherit one of the two alleles from each parent. These observations of discrete inheritance and
10005-512: The population is decreasing globally. All but five species of monitor lizards are classified by the Convention on International Trade in Endangered Species of Wild Fauna and Flora under Appendix II, which is loosely defined as species that are not necessarily threatened with extinction but may become so unless trade in such species is subject to strict regulation to avoid use incompatible with
10120-543: The process of protein production . It was discovered that the cell uses DNA as a template to create matching messenger RNA , molecules with nucleotides very similar to DNA. The nucleotide sequence of a messenger RNA is used to create an amino acid sequence in protein; this translation between nucleotide sequences and amino acid sequences is known as the genetic code . With the newfound molecular understanding of inheritance came an explosion of research. A notable theory arose from Tomoko Ohta in 1973 with her amendment to
10235-435: The product rule, the sum rule, and more. Geneticists use diagrams and symbols to describe inheritance. A gene is represented by one or a few letters. Often a "+" symbol is used to mark the usual, non-mutant allele for a gene. In fertilization and breeding experiments (and especially when discussing Mendel's laws) the parents are referred to as the "P" generation and the offspring as the "F1" (first filial) generation. When
10350-519: The properties of a protein by destabilizing the structure or changing the surface of the protein in a way that changes its interaction with other proteins and molecules. For example, sickle-cell anemia is a human genetic disease that results from a single base difference within the coding region for the β-globin section of hemoglobin, causing a single amino acid change that changes hemoglobin's physical properties. Sickle-cell versions of hemoglobin stick to themselves, stacking to form fibers that distort
10465-426: The protein itself). Protein structure is dynamic; the protein hemoglobin bends into slightly different forms as it facilitates the capture, transport, and release of oxygen molecules within mammalian blood. A single nucleotide difference within DNA can cause a change in the amino acid sequence of a protein. Because protein structures are the result of their amino acid sequences, some changes can dramatically change
10580-652: The pulmonary and systemic circuits, which in turn ensure that oxygenated blood is quickly distributed to the body without also flooding the lungs with high-pressure blood. Monitor lizards are oviparous , laying from seven to 38 eggs , which they often cover with soil or protect in a hollow tree stump. Some species, including the Komodo dragon, are capable of parthenogenesis . Anatomical and molecular studies indicate that all varanids (and possibly all lizards) are venomous . Unlike snakes, monitor lizard venom glands are situated in their lower jaw. The venom of monitor lizards
10695-406: The rate of changes in DNA are called mutagenic : mutagenic chemicals promote errors in DNA replication, often by interfering with the structure of base-pairing, while UV radiation induces mutations by causing damage to the DNA structure. Chemical damage to DNA occurs naturally as well and cells use DNA repair mechanisms to repair mismatches and breaks. The repair does not, however, always restore
10810-408: The same allele of a given gene are called homozygous at that gene locus , while organisms with two different alleles of a given gene are called heterozygous . The set of alleles for a given organism is called its genotype , while the observable traits of the organism are called its phenotype . When organisms are heterozygous at a gene, often one allele is called dominant as its qualities dominate
10925-401: The second gene epistatic to the first. Many traits are not discrete features (e.g. purple or white flowers) but are instead continuous features (e.g. human height and skin color ). These complex traits are products of many genes. The influence of these genes is mediated, to varying degrees, by the environment an organism has experienced. The degree to which an organism's genes contribute to
11040-506: The segregation of alleles are collectively known as Mendel's first law or the Law of Segregation. However, the probability of getting one gene over the other can change due to dominant, recessive, homozygous, or heterozygous genes. For example, Mendel found that if you cross heterozygous organisms your odds of getting the dominant trait is 3:1. Real geneticist study and calculate probabilities by using theoretical probabilities, empirical probabilities,
11155-653: The shape of red blood cells carrying the protein. These sickle-shaped cells no longer flow smoothly through blood vessels , having a tendency to clog or degrade, causing the medical problems associated with this disease. Some DNA sequences are transcribed into RNA but are not translated into protein products—such RNA molecules are called non-coding RNA . In some cases, these products fold into structures which are involved in critical cell functions (e.g. ribosomal RNA and transfer RNA ). RNA can also have regulatory effects through hybridization interactions with other RNA molecules (such as microRNA ). Although genes contain all
11270-400: The shape of the skull and limbs do vary, and are strongly related to the ecology of each species. Monitor lizards maintain large territories and employ active-pursuit hunting techniques that are reminiscent of similar-sized mammals. The active nature of monitor lizards has led to numerous studies on the metabolic capacities of these lizards. The general consensus is that monitor lizards have
11385-446: The similar molecule RNA instead of DNA as their genetic material. DNA normally exists as a double-stranded molecule, coiled into the shape of a double helix . Each nucleotide in DNA preferentially pairs with its partner nucleotide on the opposite strand: A pairs with T, and C pairs with G. Thus, in its two-stranded form, each strand effectively contains all necessary information, redundant with its partner strand. This structure of DNA
11500-496: The single celled alga Acetabularia . The Hershey–Chase experiment in 1952 confirmed that DNA (rather than protein) is the genetic material of the viruses that infect bacteria, providing further evidence that DNA is the molecule responsible for inheritance. James Watson and Francis Crick determined the structure of DNA in 1953, using the X-ray crystallography work of Rosalind Franklin and Maurice Wilkins that indicated DNA has
11615-731: The state since at least 1990. Genetic studies have shown that these introduced animals are part of the subpopulation that originates from West Africa, and now often is recognized as its own species, the West African Nile monitor . The vast majority of the established breeding population is in Lee County , particularly in the Cape Coral and surrounding regions, including the nearby barrier islands ( Sanibel , Captiva , and North Captiva ), Pine Island , Fort Myers , and Punta Rassa . Established populations also exist in adjacent Charlotte County , especially on Gasparilla Island . Other areas in Florida with
11730-441: The strands are separated, new partner strands can be reconstructed for each based on the sequence of the old strand. This property is what gives DNA its semi-conservative nature where one strand of new DNA is from an original parent strand. Although the structure of DNA showed how inheritance works, it was still not known how DNA influences the behavior of cells. In the following years, scientists tried to understand how DNA controls
11845-564: The study of inheritance in his inaugural address to the Third International Conference on Plant Hybridization in London in 1906. After the rediscovery of Mendel's work, scientists tried to determine which molecules in the cell were responsible for inheritance. In 1900, Nettie Stevens began studying the mealworm. Over the next 11 years, she discovered that females only had the X chromosome and males had both X and Y chromosomes. She
11960-579: The subgenus Euprepriosaurus , but as of 2016, form their own subgenus Hapturosaurus . V. jobiensis was once considered to be a member of the V. indicus species complex, but is now considered to represent its own species complex. Genus Varanus Subgenus Empagusia : Subgenus Euprepiosaurus : Subgenus Hapturosaurus : Subgenus Odatria : Subgenus Papusaurus Subgenus Philippinosaurus : Subgenus Polydaedalus : Subgenus Psammosaurus : Subgenus Solomonsaurus : Genetics Genetics
12075-609: The survival of the species in the wild. The remaining five species – the Bengal , yellow , desert , and clouded monitors and the Komodo Dragon– are classified under CITES Appendix I, which outlaws international commercial trade in the species. The yellow monitor is protected in all countries in its range except Bhutan, Nepal, India, Pakistan, and Bangladesh. In Kerala , Andhra Pradesh , Karnataka , Telangana and all other parts of South India, catching or killing of monitor lizards
12190-412: The tail and large, greenish-yellow rosette -like spots on their backs with a blackish tiny spot in the middle. Their throats and undersides are an ochre-yellow to a creamy-yellow, often with faint barring. Their nostrils are placed high on their snouts, indicating these animals are very well adapted for an aquatic lifestyle. They are also excellent climbers and quick runners on land. Nile monitors feed on
12305-536: The tryptophan synthesis process. Differences in gene expression are especially clear within multicellular organisms , where cells all contain the same genome but have very different structures and behaviors due to the expression of different sets of genes. All the cells in a multicellular organism derive from a single cell, differentiating into variant cell types in response to external and intercellular signals and gradually establishing different patterns of gene expression to create different behaviors. As no single gene
12420-482: The twenty possible amino acids in a protein or an instruction to end the amino acid sequence ; this correspondence is called the genetic code . The flow of information is unidirectional: information is transferred from nucleotide sequences into the amino acid sequence of proteins, but it never transfers from protein back into the sequence of DNA—a phenomenon Francis Crick called the central dogma of molecular biology . The specific sequence of amino acids results in
12535-545: The two is responsible for inheritance. In 1928 , Frederick Griffith discovered the phenomenon of transformation : dead bacteria could transfer genetic material to "transform" other still-living bacteria. Sixteen years later, in 1944, the Avery–MacLeod–McCarty experiment identified DNA as the molecule responsible for transformation. The role of the nucleus as the repository of genetic information in eukaryotes had been established by Hämmerling in 1943 in his work on
12650-405: The western being the West African Nile monitor and the eastern (of Central African rainforests) being moved back into the Nile monitor. As the type locality for the ornate monitor is in the Central African country of Cameroon , the scientific name V. ornatus becomes a synonym of V. niloticus . Individuals with the "ornate color pattern" and individuals with the "Nile color pattern" occur in both
12765-532: The work of the Augustinian friar Gregor Mendel in the mid-19th century. Prior to Mendel, Imre Festetics , a Hungarian noble, who lived in Kőszeg before Mendel, was the first who used the word "genetic" in hereditarian context, and is considered the first geneticist. He described several rules of biological inheritance in his work The genetic laws of nature (Die genetischen Gesetze der Natur, 1819). His second law
12880-518: Was able to conclude that sex is a chromosomal factor and is determined by the male. In 1911, Thomas Hunt Morgan argued that genes are on chromosomes , based on observations of a sex-linked white eye mutation in fruit flies . In 1913, his student Alfred Sturtevant used the phenomenon of genetic linkage to show that genes are arranged linearly on the chromosome. Although genes were known to exist on chromosomes, chromosomes are composed of both protein and DNA, and scientists did not know which of
12995-591: Was first observed by Gregor Mendel, who studied the segregation of heritable traits in pea plants, showing for example that flowers on a single plant were either purple or white—but never an intermediate between the two colors. The discrete versions of the same gene controlling the inherited appearance (phenotypes) are called alleles . In the case of the pea, which is a diploid species, each individual plant has two copies of each gene, one copy inherited from each parent. Many species, including humans, have this pattern of inheritance. Diploid organisms with two copies of
13110-421: Was particulate, not acquired, and that the inheritance patterns of many traits could be explained through simple rules and ratios. The importance of Mendel's work did not gain wide understanding until 1900, after his death, when Hugo de Vries and other scientists rediscovered his research. William Bateson , a proponent of Mendel's work, coined the word genetics in 1905. The adjective genetic , derived from
13225-529: Was the inheritance of acquired characteristics : the belief that individuals inherit traits strengthened by their parents. This theory (commonly associated with Jean-Baptiste Lamarck ) is now known to be wrong—the experiences of individuals do not affect the genes they pass to their children. Other theories included Darwin's pangenesis (which had both acquired and inherited aspects) and Francis Galton 's reformulation of pangenesis as both particulate and inherited. Modern genetics started with Mendel's studies of
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