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93-474: Jackals are canids native to Africa and Eurasia . While the word "jackal" has historically been used for many canines of the subtribe canina , in modern use it most commonly refers to three species: the closely related black-backed jackal ( Lupulella mesomelas ) and side-striped jackal ( Lupulella adusta ) of Central and Southern Africa , and the golden jackal ( Canis aureus ) of south-central Europe and Asia. The African golden wolf ( Canis lupaster )
186-522: A baculum and a structure called the bulbus glandis that expands during copulation , forming a copulatory tie that lasts for up to an hour. Young canids are born blind, with their eyes opening a few weeks after birth. All living canids (Caninae) have a ligament analogous to the nuchal ligament of ungulates used to maintain the posture of the head and neck with little active muscle exertion; this ligament allows them to conserve energy while running long distances following scent trails with their nose to
279-550: A clade . A member of this family is also called a canid ( / ˈ k eɪ n ɪ d / ). The family includes three subfamilies : the Caninae , and the extinct Borophaginae and Hesperocyoninae . The Caninae are known as canines, and include domestic dogs , wolves , coyotes , foxes , jackals and other species. Canids are found on all continents except Antarctica , having arrived independently or accompanied by human beings over extended periods of time. Canids vary in size from
372-532: A dental formula of: 3.1.4.2 3.1.4.3 . The bush dog has only one upper molar with two below, the dhole has two above and two below. and the bat-eared fox has three or four upper molars and four lower ones. The molar teeth are strong in most species, allowing the animals to crack open bone to reach the marrow . The deciduous, or baby teeth, formula in canids is 3.1.3 3.1.3 , molars being completely absent. Almost all canids are social animals and live together in groups. In general, they are territorial or have
465-562: A gestation of 50 to 60 days, while larger species average 60 to 65 days. The time of year in which the breeding season occurs is related to the length of day, as has been shown for several species that have been moved across the equator and experiences a six-month shift of phase. Domestic dogs and certain small canids in captivity may come into oestrus more often, perhaps because the photoperiod stimulus breaks down under conditions of artificial lighting. Canids have an oestrus period of 1 to 20 days, lasting one week in most species. The size of
558-455: A 'metaphase chromosome') is highly condensed and thus easiest to distinguish and study. In animal cells, chromosomes reach their highest compaction level in anaphase during chromosome segregation . Chromosomal recombination during meiosis and subsequent sexual reproduction plays a crucial role in genetic diversity . If these structures are manipulated incorrectly, through processes known as chromosomal instability and translocation ,
651-459: A cell nucleus. Chromosomes in humans can be divided into two types: autosomes (body chromosome(s)) and allosome ( sex chromosome (s)). Certain genetic traits are linked to a person's sex and are passed on through the sex chromosomes. The autosomes contain the rest of the genetic hereditary information. All act in the same way during cell division. Human cells have 23 pairs of chromosomes (22 pairs of autosomes and one pair of sex chromosomes), giving
744-592: A distinct entoconid cusp and the broadening of the talonid of the first lower molar , and the corresponding enlargement of the talon of the upper first molar and reduction of its parastyle distinguish these late Cenozoic canids and are the essential differences that identify their clade. The cat-like Feliformia and dog-like Caniformia emerged within the Carnivoramorpha around 45–42 Mya (million years ago). The Canidae first appeared in North America during
837-400: A diverse group of some 37 species ranging in size from the maned wolf with its long limbs to the short-legged bush dog. Modern canids inhabit forests, tundra, savannas, and deserts throughout tropical and temperate parts of the world. The evolutionary relationships between the species have been studied in the past using morphological approaches, but more recently, molecular studies have enabled
930-450: A group breeds and a litter of young are reared annually in an underground den. Canids communicate by scent signals and vocalizations. One canid, the domestic dog, originated from a symbiotic relationship with Upper Paleolithic humans and is one of the most widely kept domestic animals . In the history of the carnivores, the family Canidae is represented by the two extinct subfamilies designated as Hesperocyoninae and Borophaginae, and
1023-489: A higher chance of bearing a child with a chromosome disorder. Abnormal numbers of chromosomes or chromosome sets, called aneuploidy , may be lethal or may give rise to genetic disorders. Genetic counseling is offered for families that may carry a chromosome rearrangement. The gain or loss of DNA from chromosomes can lead to a variety of genetic disorders . Human examples include: Exposure of males to certain lifestyle, environmental and/or occupational hazards may increase
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#17328453637331116-487: A home range and sleep in the open, using their dens only for breeding and sometimes in bad weather. In most foxes, and in many of the true dogs, a male and female pair work together to hunt and to raise their young. Gray wolves and some of the other larger canids live in larger groups called packs . African wild dogs have packs which may consist of 20 to 40 animals and packs of fewer than about seven individuals may be incapable of successful reproduction. Hunting in packs has
1209-440: A home territory from which they drive out other conspecifics . Canids use urine scent marks to mark their food caches or warn trespassing individuals. Social behavior is also mediated by secretions from glands on the upper surface of the tail near its root and from the anal glands , preputial glands , and supracaudal glands . Canids as a group exhibit several reproductive traits that are uncommon among mammals as
1302-454: A jackal, thus it has also been called the "red jackal" or the "Simien jackal". [REDACTED] Like foxes and coyotes, jackals are often depicted as clever sorcerers in the myths and legends of their regions. They are mentioned roughly 14 times in the Bible . It is frequently used as a literary device to illustrate desolation, loneliness, and abandonment, with reference to its habit of living in
1395-422: A larger trigonid indicating a hypercarnivore and a larger talonid indicating a more omnivorous diet. Because of its low variability, the length of the lower carnassial is used to provide an estimate of a carnivore's body size. A study of the estimated bite force at the canine teeth of a large sample of living and fossil mammalian predators, when adjusted for their body mass, found that for placental mammals
1488-445: A litter varies, with from one to 16 or more pups being born. The young are born small, blind and helpless and require a long period of parental care. They are kept in a den, most often dug into the ground, for warmth and protection. When the young begin eating solid food, both parents, and often other pack members, bring food back for them from the hunt. This is most often vomited up from the adult's stomach. Where such pack involvement in
1581-480: A narrower sense, 'chromosome' can be used to refer to the individualized portions of chromatin during cell division, which are visible under light microscopy due to high condensation. The word chromosome ( / ˈ k r oʊ m ə ˌ s oʊ m , - ˌ z oʊ m / ) comes from the Greek words χρῶμα ( chroma , "colour") and σῶμα ( soma , "body"), describing the strong staining produced by particular dyes . The term
1674-424: A scavenger than a hunter; its molars appear to be adapted for crushing bones and it may have gone extinct as a result of the extinction of the large herbivorous animals on whose carcasses it relied. In 2015, a study of mitochondrial genome sequences and whole-genome nuclear sequences of African and Eurasian canids indicated that extant wolf-like canids have colonized Africa from Eurasia at least five times throughout
1767-481: A semi-ordered structure, where it is wrapped around histones (structural proteins), forming a composite material called chromatin. The packaging of DNA into nucleosomes causes a 10 nanometer fibre which may further condense up to 30 nm fibres Most of the euchromatin in interphase nuclei appears to be in the form of 30-nm fibers. Chromatin structure is the more decondensed state, i.e. the 10-nm conformation allows transcription. During interphase (the period of
1860-617: A separate species, Canis anthus ( African golden wolf ). According to a phylogeny derived from nuclear sequences, the Eurasian golden jackal ( Canis aureus ) diverged from the wolf/coyote lineage 1.9 Mya , but the African golden wolf separated 1.3 Mya. Mitochondrial genome sequences indicated the Ethiopian wolf diverged from the wolf/coyote lineage slightly prior to that. Wild canids are found on every continent except Antarctica, and inhabit
1953-418: A series of experiments beginning in the mid-1880s, Theodor Boveri gave definitive contributions to elucidating that chromosomes are the vectors of heredity , with two notions that became known as 'chromosome continuity' and 'chromosome individuality'. Wilhelm Roux suggested that every chromosome carries a different genetic configuration , and Boveri was able to test and confirm this hypothesis. Aided by
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#17328453637332046-542: A total of 46 per cell. In addition to these, human cells have many hundreds of copies of the mitochondrial genome . Sequencing of the human genome has provided a great deal of information about each of the chromosomes. Below is a table compiling statistics for the chromosomes, based on the Sanger Institute 's human genome information in the Vertebrate Genome Annotation (VEGA) database . Number of genes
2139-495: A whole. They are typically monogamous , provide paternal care to their offspring, have reproductive cycles with lengthy proestral and dioestral phases and have a copulatory tie during mating. They also retain adult offspring in the social group, suppressing the ability of these to breed while making use of the alloparental care they can provide to help raise the next generation. Most canid species are spontaneous ovulators, though maned wolves are induced ovulators . During
2232-404: A wide range of different habitats, including deserts , mountains , forests , and grasslands . They vary in size from the fennec fox, which may be as little as 24 cm (9.4 in) in length and weigh 0.6 kg (1.3 lb), to the gray wolf , which may be up to 160 cm (5.2 ft) long, and can weigh up to 79 kg (174 lb). Only a few species are arboreal —the gray fox ,
2325-577: A wolf, and Canis rufus appeared, possibly a direct descendant of C. edwardii . Around 0.8 Mya, Canis ambrusteri emerged in North America. A large wolf, it was found all over North and Central America and was eventually supplanted by the dire wolf, which then spread into South America during the Late Pleistocene. By 0.3 Mya, a number of subspecies of the gray wolf ( C. lupus ) had developed and had spread throughout Europe and northern Asia. The gray wolf colonized North America during
2418-440: Is hexaploid , having six copies of seven different chromosome types for a total of 42 chromosomes. Normal members of a particular eukaryotic species all have the same number of nuclear chromosomes. Other eukaryotic chromosomes, i.e., mitochondrial and plasmid-like small chromosomes, are much more variable in number, and there may be thousands of copies per cell. Asexually reproducing species have one set of chromosomes that are
2511-515: Is a monogamous pair, which defends its territory from other pairs by vigorously chasing intruders and marking landmarks around the territory with their urine and feces . The territory may be large enough to hold some young adults, which stay with their parents until they establish their own territories. Jackals may occasionally assemble in small packs , for example, to scavenge a carcass, but they normally hunt either alone or in pairs. The English word "jackal" dates back to 1600 and derives from
2604-413: Is an estimate, as it is in part based on gene predictions . Total chromosome length is an estimate as well, based on the estimated size of unsequenced heterochromatin regions. Based on the micrographic characteristics of size, position of the centromere and sometimes the presence of a chromosomal satellite , the human chromosomes are classified into the following groups: In general, the karyotype
2697-403: Is only used for cutting. They use their molars for grinding except for the lower first molar m1 (the lower carnassial) that has evolved for both cutting and grinding depending on the canid's dietary adaptation. On the lower carnassial, the trigonid is used for slicing and the talonid is used for grinding. The ratio between the trigonid and the talonid indicates a carnivore's dietary habits, with
2790-605: Is organized into a structure called the nucleoid . The nucleoid is a distinct structure and occupies a defined region of the bacterial cell. This structure is, however, dynamic and is maintained and remodeled by the actions of a range of histone-like proteins, which associate with the bacterial chromosome. In archaea , the DNA in chromosomes is even more organized, with the DNA packaged within structures similar to eukaryotic nucleosomes. Certain bacteria also contain plasmids or other extrachromosomal DNA . These are circular structures in
2883-544: Is present on each sister chromatid . A special DNA base sequence in the region of the kinetochores provides, along with special proteins, longer-lasting attachment in this region. The microtubules then pull the chromatids apart toward the centrosomes, so that each daughter cell inherits one set of chromatids. Once the cells have divided, the chromatids are uncoiled and DNA can again be transcribed. In spite of their appearance, chromosomes are structurally highly condensed, which enables these giant DNA structures to be contained within
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2976-415: Is probably the ancestor of modern jackals. The paraphyletic nature of Canis with respect to Lycaon and Cuon has led to suggestions that the two African jackals should be assigned to different genera, Schaeffia for the side-striped jackal and Lupulella for the black-backed jackal or Lupulella for both. The intermediate size and shape of the Ethiopian wolf has at times led it to be regarded as
3069-456: Is said she appears as jackals when meat is offered to her. The Serer religion and creation myth posits jackals were among the first animals created by Roog , the supreme deity of the Serer people . Canidae Canidae ( / ˈ k æ n ɪ d iː / ; from Latin, canis , " dog ") is a biological family of dog-like carnivorans , colloquially referred to as dogs , and constitutes
3162-413: Is significant variation within species. Often there is: Also, variation in karyotype may occur during development from the fertilized egg. The technique of determining the karyotype is usually called karyotyping . Cells can be locked part-way through division (in metaphase) in vitro (in a reaction vial) with colchicine . These cells are then stained, photographed, and arranged into a karyogram , with
3255-595: Is the African wolf ( C. lupaster ), which was once thought to be an African branch of the golden jackal. As they possess 78 chromosomes, all members of the genus Canis are karyologically indistinguishable from each other, and from the dhole and the African hunting dog. The two African jackals are shown to be the most basal members of this clade, indicating the clade's origin from Africa. Canis arnensis arrived in Mediterranean Europe 1.9 million years ago and
3348-425: Is the characteristic chromosome complement of a eukaryote species . The preparation and study of karyotypes is part of cytogenetics . Although the replication and transcription of DNA is highly standardized in eukaryotes, the same cannot be said for their karyotypes, which are often highly variable. There may be variation between species in chromosome number and in detailed organization. In some cases, there
3441-429: Is the only natural context in which individual chromosomes are visible with an optical microscope . Mitotic metaphase chromosomes are best described by a linearly organized longitudinally compressed array of consecutive chromatin loops. During mitosis, microtubules grow from centrosomes located at opposite ends of the cell and also attach to the centromere at specialized structures called kinetochores , one of which
3534-505: The Beringian land bridge allowed members of the genus Eucyon a means to enter Asia from North America and they continued on to colonize Europe. The Canis , Urocyon , and Vulpes genera developed from canids from North America , where the canine radiation began. The success of these canids was related to the development of lower carnassials that were capable of both mastication and shearing. Around 5 million years ago, some of
3627-810: The Late Eocene (37.8-33.9 Mya). They did not reach Eurasia until the Late Miocene or to South America until the Late Pliocene . This cladogram shows the phylogenetic position of canids within Caniformia , based on fossil finds: (bears, procyonids, pinnipeds, etc.) [REDACTED] (various † Miacis spp.) [REDACTED] ( Mesocyon , Enhydrocyon , Hesperocyon , and other basal canines, e.g. Cynodictis ) [REDACTED] ( Aelurodon , cynarctins , and others) [REDACTED] (all modern canids and extinct relatives) [REDACTED] The Canidae are
3720-437: The cell cycle where the cell is not dividing), two types of chromatin can be distinguished: In the early stages of mitosis or meiosis (cell division), the chromatin double helix becomes more and more condensed. They cease to function as accessible genetic material ( transcription stops) and become a compact transportable form. The loops of thirty-nanometer chromatin fibers are thought to fold upon themselves further to form
3813-502: The cytoplasm that contain cellular DNA and play a role in horizontal gene transfer . In prokaryotes and viruses, the DNA is often densely packed and organized; in the case of archaea, by homology to eukaryotic histones, and in the case of bacteria, by histone-like proteins. Bacterial chromosomes tend to be tethered to the plasma membrane of the bacteria. In molecular biology application, this allows for its isolation from plasmid DNA by centrifugation of lysed bacteria and pelleting of
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3906-451: The endosymbiotic bacteria Candidatus Hodgkinia cicadicola and Candidatus Tremblaya princeps , to more than 14,000,000 base pairs in the soil-dwelling bacterium Sorangium cellulosum . Some bacteria have more than one chromosome. For instance, Spirochaetes such as Borrelia burgdorferi (causing Lyme disease ), contain a single linear chromosome. Vibrios typically carry two chromosomes of very different size. Genomes of
3999-409: The mandible teeth . Teeth are numbered using one side of the mouth and from the front of the mouth to the back. In carnivores , the upper premolar P4 and the lower molar m1 form the carnassials that are used together in a scissor-like action to shear the muscle and tendon of prey. Canids use their premolars for cutting and crushing except for the upper fourth premolar P4 (the upper carnassial) that
4092-580: The maned wolf ( Chrysocyon brachyurus ), the short-eared dog ( Atelocynus microtis ), the bush dog ( Speothos venaticus ), the crab-eating fox ( Cerdocyon thous ), and the South American foxes ( Lycalopex spp.). The monophyly of this group has been established by molecular means. During the Pleistocene , the North American wolf line appeared, with Canis edwardii , clearly identifiable as
4185-563: The 16 chromosomes of yeast were fused into one giant chromosome, it was found that the cells were still viable with only somewhat reduced growth rates. The tables below give the total number of chromosomes (including sex chromosomes) in a cell nucleus for various eukaryotes. Most are diploid , such as humans who have 22 different types of autosomes —each present as two homologous pairs—and two sex chromosomes , giving 46 chromosomes in total. Some other organisms have more than two copies of their chromosome types, for example bread wheat which
4278-407: The 2-metre-long (6.6 ft) gray wolf to the 24-centimetre-long (9.4 in) fennec fox . The body forms of canids are similar, typically having long muzzles, upright ears, teeth adapted for cracking bones and slicing flesh, long legs, and bushy tails. They are mostly social animals , living together in family units or small groups and behaving co-operatively. Typically, only the dominant pair in
4371-621: The French chacal , itself from Turkish çakal , itself from Persian شغال shaghāl , from or cognate with Sanskrit शृगाल śṛgāla- meaning "the howler". Dog [REDACTED] Gray wolf [REDACTED] Coyote [REDACTED] Golden wolf [REDACTED] Golden jackal [REDACTED] Ethiopian wolf [REDACTED] Dhole [REDACTED] African wild dog [REDACTED] Side-striped jackal [REDACTED] Black-backed jackal [REDACTED] Similarities between jackals and coyotes led Lorenz Oken , in
4464-621: The Old World Eucyon evolved into the first members of Canis , In the Pliocene , around 4–5 Mya, Canis lepophagus appeared in North America. This was small and sometimes coyote-like. Others were wolf-like. C. latrans (the coyote) is theorized to descend from C. lepophagus . The formation of the Isthmus of Panama , about 3 Mya, joined South America to North America, allowing canids to invade South America , where they diversified. However,
4557-501: The Pliocene and Pleistocene, which is consistent with fossil evidence suggesting that much of African canid fauna diversity resulted from the immigration of Eurasian ancestors, likely coincident with Plio-Pleistocene climatic oscillations between arid and humid conditions. When comparing the African and Eurasian golden jackals, the study concluded that the African specimens represented a distinct monophyletic lineage that should be recognized as
4650-597: The advantage that larger prey items can be tackled. Some species form packs or live in small family groups depending on the circumstances, including the type of available food. In most species, some individuals live on their own. Within a canid pack, there is a system of dominance so that the strongest, most experienced animals lead the pack. In most cases, the dominant male and female are the only pack members to breed. Canids communicate with each other by scent signals , by visual clues and gestures, and by vocalizations such as growls, barks, and howls . In most cases, groups have
4743-471: The bite force at the canines was greatest in the extinct dire wolf (163), followed among the modern canids by the four hypercarnivores that often prey on animals larger than themselves: the African wild dog (142), the gray wolf (136), the dhole (112), and the dingo (108). The bite force at the carnassials showed a similar trend to the canines. A predator's largest prey size is strongly influenced by its biomechanical limits. Most canids have 42 teeth , with
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#17328453637334836-415: The cell may undergo mitotic catastrophe . This will usually cause the cell to initiate apoptosis , leading to its own death , but the process is occasionally hampered by cell mutations that result in the progression of cancer . The term 'chromosome' is sometimes used in a wider sense to refer to the individualized portions of chromatin in cells, which may or may not be visible under light microscopy. In
4929-423: The cell's nucleus. Each chromosome has one centromere , with one or two arms projecting from the centromere, although, under most circumstances, these arms are not visible as such. In addition, most eukaryotes have a small circular mitochondrial genome , and some eukaryotes may have additional small circular or linear cytoplasmic chromosomes. In the nuclear chromosomes of eukaryotes, the uncondensed DNA exists in
5022-417: The center of the cell in their condensed form. Before this stage occurs, each chromosome is duplicated ( S phase ), and the two copies are joined by a centromere —resulting in either an X-shaped structure if the centromere is located equatorially, or a two-armed structure if the centromere is located distally; the joined copies are called ' sister chromatids '. During metaphase, the duplicated structure (called
5115-438: The closely related island fox and the raccoon dog habitually climb trees. All canids have a similar basic form, as exemplified by the gray wolf, although the relative length of muzzle, limbs, ears, and tail vary considerably between species. With the exceptions of the bush dog, the raccoon dog and some domestic dog breeds , canids have relatively long legs and lithe bodies, adapted for chasing prey. The tails are bushy and
5208-507: The closest living relatives to modern humans, have 48 chromosomes as do the other great apes : in humans two chromosomes fused to form chromosome 2 . Chromosomal aberrations are disruptions in the normal chromosomal content of a cell. They can cause genetic conditions in humans, such as Down syndrome , although most aberrations have little to no effect. Some chromosome abnormalities do not cause disease in carriers, such as translocations , or chromosomal inversions , although they may lead to
5301-406: The compact metaphase chromosomes of mitotic cells. The DNA is thus condensed about ten-thousand-fold. The chromosome scaffold , which is made of proteins such as condensin , TOP2A and KIF4 , plays an important role in holding the chromatin into compact chromosomes. Loops of thirty-nanometer structure further condense with scaffold into higher order structures. This highly compact form makes
5394-503: The coyote-sized Mesocyon of the Oligocene (38–24 Mya). These early canids probably evolved for the fast pursuit of prey in a grassland habitat; they resembled modern viverrids in appearance. Hesperocyonines eventually became extinct in the middle Miocene. One of the early Hesperocyonines, the genus Hesperocyon , gave rise to Archaeocyon and Leptocyon . These branches led to the borophagine and canine radiations . Around 8 Mya,
5487-472: The ear). Prohesperocyon probably had slightly longer limbs than its predecessors, and also had parallel and closely touching toes which differ markedly from the splayed arrangements of the digits in bears . Canidae soon divided into three subfamilies, each of which diverged during the Eocene: Hesperocyoninae (about 39.74–15 Mya), Borophaginae (about 34–32 Mya), and Caninae (about 34–30 Mya;
5580-404: The extant subfamily Caninae. This subfamily includes all living canids and their most recent fossil relatives. All living canids as a group form a dental monophyletic relationship with the extinct borophagines, with both groups having a bicuspid (two points) on the lower carnassial talonid , which gives this tooth an additional ability in mastication . This, together with the development of
5673-401: The feeding of the litter occurs, the breeding success rate is higher than is the case where females split from the group and rear their pups in isolation. Young canids may take a year to mature and learn the skills they need to survive. In some species, such as the African wild dog, male offspring usually remain in the natal pack, while females disperse as a group and join another small group of
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#17328453637335766-404: The first identifiable member of the dog family had arisen. Named Prohesperocyon wilsoni , its fossils have been found in southwest Texas. The chief features which identify it as a canid include the loss of the upper third molar (part of a trend toward a more shearing bite), and the structure of the middle ear which has an enlarged bulla (the hollow bony structure protecting the delicate parts of
5859-437: The forefeet, but the pollex (thumb) is reduced and does not reach the ground. On the hind feet are four toes, but in some domestic dogs, a fifth vestigial toe, known as a dewclaw , is sometimes present, but has no anatomical connection to the rest of the foot. In some species, slightly curved nails are non-retractile and more-or-less blunt while other species have sharper, partially-retractile claws. The canine penis contains
5952-473: The genus Burkholderia carry one, two, or three chromosomes. Prokaryotic chromosomes have less sequence-based structure than eukaryotes. Bacteria typically have a one-point (the origin of replication ) from which replication starts, whereas some archaea contain multiple replication origins. The genes in prokaryotes are often organized in operons and do not usually contain introns , unlike eukaryotes. Prokaryotes do not possess nuclei. Instead, their DNA
6045-574: The genus has been changed from Thos to Canis . The wolf-like canids are a group of large carnivores that are genetically closely related. They all have 78 chromosomes . The group includes genus Canis , Cuon , and Lycaon . The members are the dog (C. lupus familiaris) , gray wolf ( C. lupus ), coyote ( C. latrans ), golden jackal ( C. aureus ), Ethiopian wolf ( C. simensis ), black-backed jackal ( C. mesomelas ), side-striped jackal ( C. adustus ), dhole ( Cuon alpinus ), and African wild dog ( Lycaon pictus ). The latest recognized member
6138-503: The gray wolf, the coyote and the red fox, for sport. Canids such as the dhole are now endangered in the wild because of persecution, habitat loss, a depletion of ungulate prey species and transmission of diseases from domestic dogs. Chromosome A chromosome is a package of DNA containing part or all of the genetic material of an organism . In most chromosomes, the very long thin DNA fibers are coated with nucleosome -forming packaging proteins ; in eukaryotic cells,
6231-491: The ground. However, based on skeletal details of the neck, at least some of the Borophaginae (such as Aelurodon ) are believed to have lacked this ligament. Dentition relates to the arrangement of teeth in the mouth, with the dental notation for the upper-jaw teeth using the upper-case letters I to denote incisors , C for canines , P for premolars , and M for molars , and the lower-case letters i, c, p and m to denote
6324-583: The independent work of Boveri and Sutton (both around 1902) by naming the chromosome theory of inheritance the ' Boveri–Sutton chromosome theory ' (sometimes known as the 'Sutton–Boveri chromosome theory'). Ernst Mayr remarks that the theory was hotly contested by some famous geneticists, including William Bateson , Wilhelm Johannsen , Richard Goldschmidt and T.H. Morgan , all of a rather dogmatic mindset. Eventually, absolute proof came from chromosome maps in Morgan's own laboratory. The number of human chromosomes
6417-460: The individual chromosomes visible, and they form the classic four-arm structure, a pair of sister chromatids attached to each other at the centromere . The shorter arms are called p arms (from the French petit , small) and the longer arms are called q arms ( q follows p in the Latin alphabet; q-g "grande"; alternatively it is sometimes said q is short for queue meaning tail in French ). This
6510-605: The investigation of phylogenetics relationships. In some species, genetic divergence has been suppressed by the high level of gene flow between different populations and where the species have hybridized, large hybrid zones exist. Carnivorans evolved after the extinction of the non-avian dinosaurs 66 million years ago. Around 50 million years ago, or earlier, in the Paleocene , the Carnivora split into two main divisions: caniform (dog-like) and feliform (cat-like). By 40 Mya,
6603-545: The last common ancestor of the South American canids lived in North America some 4 Mya and more than one incursion across the new land bridge is likely given the fact that more than one lineage is present in South America. Two North American lineages found in South America are the gray fox ( Urocyon cinereoargentus ) and the now-extinct dire wolf ( Aenocyon dirus ). Besides these, there are species endemic to South America:
6696-484: The late Rancholabrean era across the Bering land bridge, with at least three separate invasions, with each one consisting of one or more different Eurasian gray wolf clades. MtDNA studies have shown that there are at least four extant C. lupus lineages. The dire wolf shared its habitat with the gray wolf, but became extinct in a large-scale extinction event that occurred around 11,500 years ago. It may have been more of
6789-545: The length and quality of the pelage vary with the season. The muzzle portion of the skull is much more elongated than that of the cat family. The zygomatic arches are wide, there is a transverse lambdoidal ridge at the rear of the cranium and in some species, a sagittal crest running from front to back. The bony orbits around the eye never form a complete ring and the auditory bullae are smooth and rounded. Females have three to seven pairs of mammae . All canids are digitigrade , meaning they walk on their toes. The tip of
6882-494: The matching chromosomes of father and mother can exchange small parts of themselves ( crossover ) and thus create new chromosomes that are not inherited solely from either parent. When a male and a female gamete merge during fertilization , a new diploid organism is formed. Some animal and plant species are polyploid [Xn], having more than two sets of homologous chromosomes . Important crops such as tobacco or wheat are often polyploid, compared to their ancestral species. Wheat has
6975-429: The membranes (and the attached DNA). Prokaryotic chromosomes and plasmids are, like eukaryotic DNA, generally supercoiled . The DNA must first be released into its relaxed state for access for transcription , regulation, and replication . Each eukaryotic chromosome consists of a long linear DNA molecule associated with proteins , forming a compact complex of proteins and DNA called chromatin . Chromatin contains
7068-456: The most important of these proteins are the histones . Aided by chaperone proteins , the histones bind to and condense the DNA molecule to maintain its integrity. These eukaryotic chromosomes display a complex three-dimensional structure that has a significant role in transcriptional regulation . Normally, chromosomes are visible under a light microscope only during the metaphase of cell division , where all chromosomes are aligned in
7161-483: The nose is always naked, as are the cushioned pads on the soles of the feet. These latter consist of a single pad behind the tip of each toe and a more-or-less three-lobed central pad under the roots of the digits. Hairs grow between the pads and in the Arctic fox the sole of the foot is densely covered with hair at some times of the year. With the exception of the four-toed African wild dog ( Lycaon pictus ), five toes are on
7254-526: The only surviving subfamily). Members of each subfamily showed an increase in body mass with time and some exhibited specialized hypercarnivorous diets that made them prone to extinction. By the Oligocene , all three subfamilies (Hesperocyoninae, Borophaginae, and Caninae) had appeared in the fossil record of North America. The earliest and most primitive branch of the Canidae was Hesperocyoninae, which included
7347-544: The opposite sex to form a new pack. One canid, the domestic dog , entered into a partnership with humans a long time ago. The dog was the first domesticated species. The archaeological record shows the first undisputed dog remains buried beside humans 14,700 years ago, with disputed remains occurring 36,000 years ago. These dates imply that the earliest dogs arose in the time of human hunter-gatherers and not agriculturists . The fact that wolves are pack animals with cooperative social structures may have been
7440-558: The proestral period, increased levels of estradiol make the female attractive to the male. There is a rise in progesterone during the estral phase when female is receptive. Following this, the level of estradiol fluctuates and there is a lengthy dioestrous phase during which the female is pregnant. Pseudo-pregnancy often occurs in canids that have ovulated but failed to conceive. A period of anestrus follows pregnancy or pseudo-pregnancy, there being only one oestral period during each breeding season. Small and medium-sized canids mostly have
7533-613: The reason that the relationship developed. Humans benefited from the canid's loyalty, cooperation, teamwork, alertness and tracking abilities, while the wolf may have benefited from the use of weapons to tackle larger prey and the sharing of food. Humans and dogs may have evolved together. Among canids, only the gray wolf has widely been known to prey on humans. Nonetheless, at least two records of coyotes killing humans have been published, and at least two other reports of golden jackals killing children. Human beings have trapped and hunted some canid species for their fur and some, especially
7626-547: The rediscovery at the start of the 1900s of Gregor Mendel 's earlier experimental work, Boveri identified the connection between the rules of inheritance and the behaviour of the chromosomes. Two generations of American cytologists were influenced by Boveri: Edmund Beecher Wilson , Nettie Stevens , Walter Sutton and Theophilus Painter (Wilson, Stevens, and Painter actually worked with him). In his famous textbook, The Cell in Development and Heredity , Wilson linked together
7719-405: The rest of Canis could justify a subdivision of that genus. In practice, Cabrera chose the undivided-genus alternative and referred to the jackals as Canis instead of Thos . Oken's Thos theory was revived in 1914 by Edmund Heller , who embraced the separate genus theory. Heller's names and the designations he gave to various jackal species and subspecies live on in current taxonomy, although
7812-486: The risk of aneuploid spermatozoa. In particular, risk of aneuploidy is increased by tobacco smoking, and occupational exposure to benzene, insecticides, and perfluorinated compounds. Increased aneuploidy is often associated with increased DNA damage in spermatozoa. The number of chromosomes in eukaryotes is highly variable. It is possible for chromosomes to fuse or break and thus evolve into novel karyotypes. Chromosomes can also be fused artificially. For example, when
7905-580: The ruins of former cities and other areas abandoned by humans. It is called "wild dog" in several translations of the Bible. In the King James Bible , Isaiah 13:21 refers to 'doleful creatures', which some commentators suggest are either jackals or hyenas . In the Indian Panchatantra stories, the jackal is mentioned as wily and wise. In Bengali tantrik tradition, they represent the goddess Kali . It
7998-438: The same in all body cells. However, asexual species can be either haploid or diploid. Sexually reproducing species have somatic cells (body cells) that are diploid [2n], having two sets of chromosomes (23 pairs in humans), one set from the mother and one from the father. Gametes (reproductive cells) are haploid [n], having one set of chromosomes. Gametes are produced by meiosis of a diploid germline cell, during which
8091-594: The set of chromosomes arranged, autosomes in order of length, and sex chromosomes (here X/Y) at the end. Like many sexually reproducing species, humans have special gonosomes (sex chromosomes, in contrast to autosomes ). These are XX in females and XY in males. Investigation into the human karyotype took many years to settle the most basic question: How many chromosomes does a normal diploid human cell contain? In 1912, Hans von Winiwarter reported 47 chromosomes in spermatogonia and 48 in oogonia , concluding an XX/XO sex determination mechanism . In 1922, Painter
8184-435: The third volume of his Lehrbuch der Naturgeschichte (1815), to place these species into a new separate genus, Thos , named after the classical Greek word θώς "jackal", but his theory had little immediate impact on taxonomy at the time. Angel Cabrera , in his 1932 monograph on the mammals of Morocco , questioned whether or not the presence of a cingulum on the upper molars of the jackals and its corresponding absence in
8277-459: The vast majority of the DNA in an organism, but a small amount inherited maternally can be found in the mitochondria . It is present in most cells , with a few exceptions, for example, red blood cells . Histones are responsible for the first and most basic unit of chromosome organization, the nucleosome . Eukaryotes ( cells with nuclei such as those found in plants, fungi, and animals) possess multiple large linear chromosomes contained in
8370-588: Was also formerly considered a jackal. While they do not form a monophyletic clade , all jackals are opportunistic omnivores, predators of small to medium-sized animals and proficient scavengers . Their long legs and curved canine teeth are adapted for hunting small mammals , birds, and reptiles , and their large feet and fused leg bones give them a physique well-suited for long-distance running, capable of maintaining speeds of 16 km/h (10 mph) for extended periods of time. Jackals are crepuscular , most active at dawn and dusk. Their most common social unit
8463-478: Was coined by the German anatomist Heinrich Wilhelm Waldeyer , referring to the term ' chromatin ', which was introduced by Walther Flemming . Some of the early karyological terms have become outdated. For example, 'chromatin' (Flemming 1880) and 'chromosom' (Waldeyer 1888) both ascribe color to a non-colored state. Otto Bütschli was the first scientist to recognize the structures now known as chromosomes. In
8556-440: Was not certain whether the diploid number of man is 46 or 48, at first favouring 46. He revised his opinion later from 46 to 48, and he correctly insisted on humans having an XX/XY system. New techniques were needed to definitively solve the problem: It took until 1954 before the human diploid number was confirmed as 46. Considering the techniques of Winiwarter and Painter, their results were quite remarkable. Chimpanzees ,
8649-544: Was published by Painter in 1923. By inspection through a microscope, he counted 24 pairs of chromosomes, giving 48 in total. His error was copied by others, and it was not until 1956 that the true number (46) was determined by Indonesian-born cytogeneticist Joe Hin Tjio . The prokaryotes – bacteria and archaea – typically have a single circular chromosome . The chromosomes of most bacteria (also called genophores ), can range in size from only 130,000 base pairs in
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