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104-405: Robert Julyan's The Place Names of New Mexico notes that "bear" names throughout New Mexico frequently come from a particular incident with a bear rather than a general abundance of bears because "any encounter with a bear likely would have been memorable." Even so, the range is currently home to black bears, and grizzly bears were once found the area as well. Basham noted in his report documenting

208-445: A buffer to recruit or titrate ions or antibiotics. Extracellular DNA acts as a functional extracellular matrix component in the biofilms of several bacterial species. It may act as a recognition factor to regulate the attachment and dispersal of specific cell types in the biofilm; it may contribute to biofilm formation; and it may contribute to the biofilm's physical strength and resistance to biological stress. Cell-free fetal DNA

312-459: A cell makes up its genome ; the human genome has approximately 3 billion base pairs of DNA arranged into 46 chromosomes. The information carried by DNA is held in the sequence of pieces of DNA called genes . Transmission of genetic information in genes is achieved via complementary base pairing. For example, in transcription, when a cell uses the information in a gene, the DNA sequence is copied into

416-450: A chain by covalent bonds (known as the phosphodiester linkage ) between the sugar of one nucleotide and the phosphate of the next, resulting in an alternating sugar-phosphate backbone . The nitrogenous bases of the two separate polynucleotide strands are bound together, according to base pairing rules (A with T and C with G), with hydrogen bonds to make double-stranded DNA. The complementary nitrogenous bases are divided into two groups,

520-445: A complementary RNA sequence through the attraction between the DNA and the correct RNA nucleotides. Usually, this RNA copy is then used to make a matching protein sequence in a process called translation , which depends on the same interaction between RNA nucleotides. In an alternative fashion, a cell may copy its genetic information in a process called DNA replication . The details of these functions are covered in other articles; here

624-492: A double helix can thus be pulled apart like a zipper, either by a mechanical force or high temperature . As a result of this base pair complementarity, all the information in the double-stranded sequence of a DNA helix is duplicated on each strand, which is vital in DNA replication. This reversible and specific interaction between complementary base pairs is critical for all the functions of DNA in organisms. Most DNA molecules are actually two polymer strands, bound together in

728-428: A full set of the mitochondrial genes. Each human mitochondrion contains, on average, approximately 5 such mtDNA molecules. Each human cell contains approximately 100 mitochondria, giving a total number of mtDNA molecules per human cell of approximately 500. However, the amount of mitochondria per cell also varies by cell type, and an egg cell can contain 100,000 mitochondria, corresponding to up to 1,500,000 copies of

832-439: A helical fashion by noncovalent bonds; this double-stranded (dsDNA) structure is maintained largely by the intrastrand base stacking interactions, which are strongest for G,C stacks. The two strands can come apart—a process known as melting—to form two single-stranded DNA (ssDNA) molecules. Melting occurs at high temperatures, low salt and high pH (low pH also melts DNA, but since DNA is unstable due to acid depurination, low pH

936-571: A higher number is also possible but this would be against the natural principle of least effort . The phosphate groups of DNA give it similar acidic properties to phosphoric acid and it can be considered as a strong acid . It will be fully ionized at a normal cellular pH, releasing protons which leave behind negative charges on the phosphate groups. These negative charges protect DNA from breakdown by hydrolysis by repelling nucleophiles which could hydrolyze it. Pure DNA extracted from cells forms white, stringy clumps. The expression of genes

1040-462: A long groove called a "flute". The spear points would typically be made by chipping a single flake from each side of the point. The point was then tied onto a spear of wood or bone. As the environment changed with the ice age ending around 17–13 Ka BP on short, and around 25–27 Ka BP on the long, many animals migrated overland to take advantage of the new sources of food. Humans following these animals, such as bison, mammoth and mastodon, thus gained

1144-667: A long-standing puzzle known as the " C-value enigma ". However, some DNA sequences that do not code protein may still encode functional non-coding RNA molecules, which are involved in the regulation of gene expression . Some noncoding DNA sequences play structural roles in chromosomes. Telomeres and centromeres typically contain few genes but are important for the function and stability of chromosomes. An abundant form of noncoding DNA in humans are pseudogenes , which are copies of genes that have been disabled by mutation. These sequences are usually just molecular fossils , although they can occasionally serve as raw genetic material for

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1248-537: A much wider geographical distribution, but mostly in the central and southern part of the continent. The haplogroup most commonly associated with Amerindian genetics is Haplogroup Q-M3 . Y-DNA , like ( mtDNA ), differs from other nuclear chromosomes in that the majority of the Y chromosome is unique and does not recombine during meiosis . This allows the historical pattern of mutations to be easily studied. The pattern indicates Indigenous Amerindians experienced two very distinctive genetic episodes: first with

1352-409: A narrower, deeper major groove. The A form occurs under non-physiological conditions in partly dehydrated samples of DNA, while in the cell it may be produced in hybrid pairings of DNA and RNA strands, and in enzyme-DNA complexes. Segments of DNA where the bases have been chemically modified by methylation may undergo a larger change in conformation and adopt the Z form . Here, the strands turn about

1456-442: A radius of 10 Å (1.0 nm). According to another study, when measured in a different solution, the DNA chain measured 22–26 Å (2.2–2.6 nm) wide, and one nucleotide unit measured 3.3 Å (0.33 nm) long. The buoyant density of most DNA is 1.7g/cm . DNA does not usually exist as a single strand, but instead as a pair of strands that are held tightly together. These two long strands coil around each other, in

1560-416: A second protein when read in the opposite direction along the other strand. In bacteria , this overlap may be involved in the regulation of gene transcription, while in viruses, overlapping genes increase the amount of information that can be encoded within the small viral genome. DNA can be twisted like a rope in a process called DNA supercoiling . With DNA in its "relaxed" state, a strand usually circles

1664-445: A simple TTAGGG sequence. These guanine-rich sequences may stabilize chromosome ends by forming structures of stacked sets of four-base units, rather than the usual base pairs found in other DNA molecules. Here, four guanine bases, known as a guanine tetrad , form a flat plate. These flat four-base units then stack on top of each other to form a stable G-quadruplex structure. These structures are stabilized by hydrogen bonding between

1768-946: A single animal species: the bison (an early cousin of the American bison ). The earliest known of these bison-oriented hunting traditions is the Folsom tradition . Folsom peoples traveled in small family groups for most of the year, returning yearly to the same springs and other favored locations on higher ground. There they would camp for a few days, perhaps erecting a temporary shelter, making and/or repairing some stone tools, or processing some meat, then moving on. Paleo-Indians were not numerous, and population densities were quite low. Paleo-Indians are generally classified by lithic reduction or lithic core "styles" and by regional adaptations. Lithic technology fluted spear points, like other spear points, are collectively called projectile points . The projectiles are constructed from chipped stones that have

1872-489: A variety of flora. Paleo-Indian groups were efficient hunters and carried a variety of tools. These included highly efficient fluted-style spear points, as well as microblades used for butchering and hide processing. Projectile points and hammerstones made from many sources are found traded or moved to new locations. Stone tools were traded and/or left behind from North Dakota and Northwest Territories , to Montana and Wyoming . Trade routes also have been found from

1976-447: Is called intercalation . Most intercalators are aromatic and planar molecules; examples include ethidium bromide , acridines , daunomycin , and doxorubicin . For an intercalator to fit between base pairs, the bases must separate, distorting the DNA strands by unwinding of the double helix. This inhibits both transcription and DNA replication, causing toxicity and mutations. As a result, DNA intercalators may be carcinogens , and in

2080-435: Is called a polynucleotide . The backbone of the DNA strand is made from alternating phosphate and sugar groups. The sugar in DNA is 2-deoxyribose , which is a pentose (five- carbon ) sugar. The sugars are joined by phosphate groups that form phosphodiester bonds between the third and fifth carbon atoms of adjacent sugar rings. These are known as the 3′-end (three prime end), and 5′-end (five prime end) carbons,

2184-434: Is dependent on ionic strength and the concentration of DNA. As a result, it is both the percentage of GC base pairs and the overall length of a DNA double helix that determines the strength of the association between the two strands of DNA. Long DNA helices with a high GC -content have more strongly interacting strands, while short helices with high AT content have more weakly interacting strands. In biology, parts of

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2288-411: Is influenced by how the DNA is packaged in chromosomes, in a structure called chromatin . Base modifications can be involved in packaging, with regions that have low or no gene expression usually containing high levels of methylation of cytosine bases. DNA packaging and its influence on gene expression can also occur by covalent modifications of the histone protein core around which DNA is wrapped in

2392-432: Is introduced by enzymes called topoisomerases . These enzymes are also needed to relieve the twisting stresses introduced into DNA strands during processes such as transcription and DNA replication . DNA exists in many possible conformations that include A-DNA , B-DNA , and Z-DNA forms, although only B-DNA and Z-DNA have been directly observed in functional organisms. The conformation that DNA adopts depends on

2496-422: Is nothing special about the four natural nucleobases that evolved on Earth. On the other hand, DNA is tightly related to RNA which does not only act as a transcript of DNA but also performs as molecular machines many tasks in cells. For this purpose it has to fold into a structure. It has been shown that to allow to create all possible structures at least four bases are required for the corresponding RNA , while

2600-432: Is one of four types of nucleobases (or bases ). It is the sequence of these four nucleobases along the backbone that encodes genetic information. RNA strands are created using DNA strands as a template in a process called transcription , where DNA bases are exchanged for their corresponding bases except in the case of thymine (T), for which RNA substitutes uracil (U). Under the genetic code , these RNA strands specify

2704-514: Is rarely used). The stability of the dsDNA form depends not only on the GC -content (% G,C basepairs) but also on sequence (since stacking is sequence specific) and also length (longer molecules are more stable). The stability can be measured in various ways; a common way is the melting temperature (also called T m value), which is the temperature at which 50% of the double-strand molecules are converted to single-strand molecules; melting temperature

2808-428: Is recreated by an enzyme called DNA polymerase . This enzyme makes the complementary strand by finding the correct base through complementary base pairing and bonding it onto the original strand. As DNA polymerases can only extend a DNA strand in a 5′ to 3′ direction, different mechanisms are used to copy the antiparallel strands of the double helix. In this way, the base on the old strand dictates which base appears on

2912-516: Is the largest human chromosome with approximately 220 million base pairs , and would be 85 mm long if straightened. In eukaryotes , in addition to nuclear DNA , there is also mitochondrial DNA (mtDNA) which encodes certain proteins used by the mitochondria. The mtDNA is usually relatively small in comparison to the nuclear DNA. For example, the human mitochondrial DNA forms closed circular molecules, each of which contains 16,569 DNA base pairs, with each such molecule normally containing

3016-486: Is to allow the cell to replicate chromosome ends using the enzyme telomerase , as the enzymes that normally replicate DNA cannot copy the extreme 3′ ends of chromosomes. These specialized chromosome caps also help protect the DNA ends, and stop the DNA repair systems in the cell from treating them as damage to be corrected. In human cells , telomeres are usually lengths of single-stranded DNA containing several thousand repeats of

3120-469: The British Columbia Interior to the coast of California . The glaciers that covered the northern half of the continent began to gradually melt, exposing new land for occupation around 17,500–14,500 years ago. At the same time as this was occurring, worldwide extinctions among the large mammals began. In North America, camelids and equids eventually died off, the latter not to reappear on

3224-657: The DNA sequence . Mutagens include oxidizing agents , alkylating agents and also high-energy electromagnetic radiation such as ultraviolet light and X-rays . The type of DNA damage produced depends on the type of mutagen. For example, UV light can damage DNA by producing thymine dimers , which are cross-links between pyrimidine bases. On the other hand, oxidants such as free radicals or hydrogen peroxide produce multiple forms of damage, including base modifications, particularly of guanosine, and double-strand breaks. A typical human cell contains about 150,000 bases that have suffered oxidative damage. Of these oxidative lesions,

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3328-501: The Gulf of Venezuela to the high mountains and valleys. The population using them were hunter-gatherers that seemed to remain within a certain circumscribed territory. El Jobo points were probably the earliest, going back to c.  14,200  – c.  12,980 BP and they were used for hunting large mammals. In contrast, the fish-tail points, dating to c. 11,000 B.P. in Patagonia , had

3432-850: The Laurentide and Cordilleran ice sheets . An alternative proposed scenario involves migration, either on foot or using boats , down the Pacific coast to South America. Evidence of the latter would have been submerged by a sea-level rise of more than a hundred meters following the end of the Last Glacial Period . The time range of the peopling of the Americas remains a source of substantial debate. Conventional estimates have it that humans reached North America at some point between 15,000 and 20,000 years ago. However, some groups of humans may have reached South America as early as 25,000 years ago. One of

3536-629: The Pacific coast and valleys of North America . This allowed land animals, followed by humans, to migrate south into the interior of the continent. The people went on foot or used boats along the coastline. The dates and routes of the peopling of the Americas remain subjects of ongoing debate. It is likely there were three waves of ancient settlers from the Bering Sea to the America continent. Stone tools , particularly projectile points and scrapers , are

3640-406: The amino-acid sequences of proteins is determined by the rules of translation , known collectively as the genetic code . The genetic code consists of three-letter 'words' called codons formed from a sequence of three nucleotides (e.g. ACT, CAG, TTT). In transcription, the codons of a gene are copied into messenger RNA by RNA polymerase . This RNA copy is then decoded by a ribosome that reads

3744-469: The cell nucleus as nuclear DNA , and some in the mitochondria as mitochondrial DNA or in chloroplasts as chloroplast DNA . In contrast, prokaryotes ( bacteria and archaea ) store their DNA only in the cytoplasm , in circular chromosomes . Within eukaryotic chromosomes, chromatin proteins, such as histones , compact and organize DNA. These compacting structures guide the interactions between DNA and other proteins, helping control which parts of

3848-556: The giant beaver , steppe wisent , giant muskox , mastodon , woolly mammoth and ancient reindeer . The Clovis culture , appearing around 11,500 BCE ( c.  13,500 BP) in North America, is one of the most notable Paleo-Indian archaeological cultures. It has been disputed whether the Clovis culture were specialist big-game hunters or employed a mixed foraging strategy that included smaller terrestrial game, aquatic animals, and

3952-685: The lithic period in the Western Hemisphere and is distinct from the term Paleolithic . Traditional theories suggest that big-animal hunters crossed the Bering Strait from North Asia into the Americas over a land bridge ( Beringia ). This bridge existed from 45,000 to 12,000 BCE (47,000–14,000 BP ). Small isolated groups of hunter-gatherers migrated alongside herds of large herbivores far into Alaska . From c.  16,500  – c.  13,500 BCE ( c.  18,500  – c.  15,500 BP), ice-free corridors developed along

4056-419: The 3′ and 5′ carbons along the sugar-phosphate backbone confers directionality (sometimes called polarity) to each DNA strand. In a nucleic acid double helix , the direction of the nucleotides in one strand is opposite to their direction in the other strand: the strands are antiparallel . The asymmetric ends of DNA strands are said to have a directionality of five prime end (5′ ), and three prime end (3′), with

4160-588: The 5′ end having a terminal phosphate group and the 3′ end a terminal hydroxyl group. One major difference between DNA and RNA is the sugar, with the 2-deoxyribose in DNA being replaced by the related pentose sugar ribose in RNA. The DNA double helix is stabilized primarily by two forces: hydrogen bonds between nucleotides and base-stacking interactions among aromatic nucleobases. The four bases found in DNA are adenine ( A ), cytosine ( C ), guanine ( G ) and thymine ( T ). These four bases are attached to

4264-516: The Americas becoming extinct towards the end of the Paleoindian period as part of the Late Pleistocene megafauna extinctions . The potential role of human hunting in the extinctions has been the subject of much controversy. From 8000 to 7000 BCE (10,000–9,000 BP) the climate stabilized, leading to a rise in population and lithic technology advances, resulting in a more sedentary lifestyle during

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4368-928: The Americas suggest that Clovis (thus the "Paleo-Indians") time range should be re-examined. In particular, sites such as Cooper's Ferry in Idaho, Cactus Hill in Virginia , Meadowcroft Rockshelter in Pennsylvania , Bear Spirit Mountain in West Virginia , Catamarca and Salta in Argentina , Pilauco and Monte Verde in Chile , Topper in South Carolina , and Quintana Roo in Mexico have generated early dates for wide-ranging Paleo-Indian occupation. Some sites significantly predate

4472-655: The Americas ;portal DNA Deoxyribonucleic acid ( / d iː ˈ ɒ k s ɪ ˌ r aɪ b oʊ nj uː ˌ k l iː ɪ k , - ˌ k l eɪ -/ ; DNA ) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix . The polymer carries genetic instructions for the development, functioning, growth and reproduction of all known organisms and many viruses . DNA and ribonucleic acid (RNA) are nucleic acids . Alongside proteins , lipids and complex carbohydrates ( polysaccharides ), nucleic acids are one of

4576-430: The Americas. Due to the evidence that Paleoindians hunted now extinct megafauna (large animals), and that following a period of overlap, most large animals across the Americas became extinct as part of the Late Pleistocene megafauna extinctions , it has been argued by many authors that hunting by Paleoindians was an important factor in the extinctions, though this suggestion is controversial, with other authors placing

4680-435: The DNA are transcribed. DNA is a long polymer made from repeating units called nucleotides . The structure of DNA is dynamic along its length, being capable of coiling into tight loops and other shapes. In all species it is composed of two helical chains, bound to each other by hydrogen bonds . Both chains are coiled around the same axis, and have the same pitch of 34 ångströms (3.4  nm ). The pair of chains have

4784-453: The DNA double helix that need to separate easily, such as the TATAAT Pribnow box in some promoters , tend to have a high AT content, making the strands easier to pull apart. In the laboratory, the strength of this interaction can be measured by finding the melting temperature T m necessary to break half of the hydrogen bonds. When all the base pairs in a DNA double helix melt,

4888-677: The Early Archaic period in some regions. Sites in Alaska (eastern Beringia) exhibit some of the earliest evidence of Paleo-Indians, followed by archaeological sites in northern British Columbia , western Alberta and the Old Crow Flats region of the Yukon territory. The Paleo-Indians would eventually flourish all over the Americas. These peoples were spread over a wide geographical area; thus there were regional variations in lifestyles. However, all

4992-401: The RNA sequence by base-pairing the messenger RNA to transfer RNA , which carries amino acids. Since there are 4 bases in 3-letter combinations, there are 64 possible codons (4  combinations). These encode the twenty standard amino acids , giving most amino acids more than one possible codon. There are also three 'stop' or 'nonsense' codons signifying the end of the coding region; these are

5096-488: The TAG, TAA, and TGA codons, (UAG, UAA, and UGA on the mRNA). Cell division is essential for an organism to grow, but, when a cell divides, it must replicate the DNA in its genome so that the two daughter cells have the same genetic information as their parent. The double-stranded structure of DNA provides a simple mechanism for DNA replication . Here, the two strands are separated and then each strand's complementary DNA sequence

5200-582: The Y lineage specific to South America indicates that certain Amerindian populations have been isolated since the initial colonization of the region. The Na-Dené , Inuit and Indigenous Alaskan populations, however, exhibit haplogroup Q (Y-DNA) mutations that are distinct from other Amerindians with various mtDNA mutations. This suggests that the earliest migrants into the northern extremes of North America and Greenland derived from later migrant populations. Evidence from full genomic studies suggests that

5304-559: The archeological history of the Cibola's Magdalena Ranger District that “[t]he heritage resources on the district are diverse and representative of nearly every prominent human evolutionary event known to anthropology. Evidence for human use of district lands date back 14,000 years to the Paleoindian period providing glimpses into the peopling of the New World and megafaunal extinction .“ Much of

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5408-442: The axis of the double helix once every 10.4 base pairs, but if the DNA is twisted the strands become more tightly or more loosely wound. If the DNA is twisted in the direction of the helix, this is positive supercoiling, and the bases are held more tightly together. If they are twisted in the opposite direction, this is negative supercoiling, and the bases come apart more easily. In nature, most DNA has slight negative supercoiling that

5512-613: The blame on climatic change. In a 2012 survey of archaeologists in The SAA Archaeological Record, 63% of respondents said that megafauna extinctions were likely the result of a "combination of factors". The Archaic period in the Americas saw a changing environment featuring a warmer, more arid climate and the disappearance of the last megafauna. The majority of population groups at this time were still highly mobile hunter-gatherers, but now individual groups started to focus on resources available to them locally. Thus with

5616-407: The canonical bases plus uracil. Twin helical strands form the DNA backbone. Another double helix may be found tracing the spaces, or grooves, between the strands. These voids are adjacent to the base pairs and may provide a binding site . As the strands are not symmetrically located with respect to each other, the grooves are unequally sized. The major groove is 22 ångströms (2.2 nm) wide, while

5720-467: The case of thalidomide, a teratogen . Others such as benzo[ a ]pyrene diol epoxide and aflatoxin form DNA adducts that induce errors in replication. Nevertheless, due to their ability to inhibit DNA transcription and replication, other similar toxins are also used in chemotherapy to inhibit rapidly growing cancer cells. DNA usually occurs as linear chromosomes in eukaryotes , and circular chromosomes in prokaryotes . The set of chromosomes in

5824-581: The cell (see below) , but the major and minor grooves are always named to reflect the differences in width that would be seen if the DNA was twisted back into the ordinary B form . In a DNA double helix, each type of nucleobase on one strand bonds with just one type of nucleobase on the other strand. This is called complementary base pairing . Purines form hydrogen bonds to pyrimidines, with adenine bonding only to thymine in two hydrogen bonds, and cytosine bonding only to guanine in three hydrogen bonds. This arrangement of two nucleotides binding together across

5928-619: The chromatin structure or else by remodeling carried out by chromatin remodeling complexes (see Chromatin remodeling ). There is, further, crosstalk between DNA methylation and histone modification, so they can coordinately affect chromatin and gene expression. For one example, cytosine methylation produces 5-methylcytosine , which is important for X-inactivation of chromosomes. The average level of methylation varies between organisms—the worm Caenorhabditis elegans lacks cytosine methylation, while vertebrates have higher levels, with up to 1% of their DNA containing 5-methylcytosine. Despite

6032-476: The conditions found in cells, it is not a well-defined conformation but a family of related DNA conformations that occur at the high hydration levels present in cells. Their corresponding X-ray diffraction and scattering patterns are characteristic of molecular paracrystals with a significant degree of disorder. Compared to B-DNA, the A-DNA form is a wider right-handed spiral, with a shallow, wide minor groove and

6136-565: The continent until the Spanish reintroduced the horse near the end of the 15th century CE. As the Quaternary extinction event was happening, the late Paleo-Indians would have relied more on other means of subsistence. From c.  10,500  – c.  9,500 BCE ( c.  12,500  – c.  11,500 BP), the broad-spectrum big game hunters of the Great Plains began to focus on

6240-405: The creation of new genes through the process of gene duplication and divergence . A gene is a sequence of DNA that contains genetic information and can influence the phenotype of an organism. Within a gene, the sequence of bases along a DNA strand defines a messenger RNA sequence, which then defines one or more protein sequences. The relationship between the nucleotide sequences of genes and

6344-449: The cytoplasm called the nucleoid . The genetic information in a genome is held within genes, and the complete set of this information in an organism is called its genotype . A gene is a unit of heredity and is a region of DNA that influences a particular characteristic in an organism. Genes contain an open reading frame that can be transcribed, and regulatory sequences such as promoters and enhancers , which control transcription of

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6448-405: The double helix (from six-carbon ring to six-carbon ring) is called a Watson-Crick base pair. DNA with high GC-content is more stable than DNA with low GC -content. A Hoogsteen base pair (hydrogen bonding the 6-carbon ring to the 5-carbon ring) is a rare variation of base-pairing. As hydrogen bonds are not covalent , they can be broken and rejoined relatively easily. The two strands of DNA in

6552-442: The edges of the bases and chelation of a metal ion in the centre of each four-base unit. Other structures can also be formed, with the central set of four bases coming from either a single strand folded around the bases, or several different parallel strands, each contributing one base to the central structure. In addition to these stacked structures, telomeres also form large loop structures called telomere loops, or T-loops. Here,

6656-481: The end of an otherwise complementary double-strand of DNA. However, branched DNA can occur if a third strand of DNA is introduced and contains adjoining regions able to hybridize with the frayed regions of the pre-existing double-strand. Although the simplest example of branched DNA involves only three strands of DNA, complexes involving additional strands and multiple branches are also possible. Branched DNA can be used in nanotechnology to construct geometric shapes, see

6760-573: The few areas of agreement is the origin from Siberia , with widespread habitation of the Americas during the end of the Last Glacial Period, and more specifically after the end of the Last Glacial Maximum around 16,000 to 13,000 years before present. The Palaeoindian culture lasts 4000 years, from 12,000 to 8000 BP. It is divided into Early Palaeoindian (12,000-10,000 BP) and Late Palaeoindian (10,000-8000 BP), ending with early events of

6864-498: The first people in the Americas diverged from Ancient East Asians about 36,000 years ago and expanded northwards into Siberia, where they encountered and interacted with a different Paleolithic Siberian population (known as Ancient North Eurasians ), giving rise to both Paleosiberian peoples and Ancient Native Americans , which later migrated towards the Beringian region, became isolated from other populations, and subsequently populated

6968-418: The focus is on the interactions between DNA and other molecules that mediate the function of the genome. Genomic DNA is tightly and orderly packed in the process called DNA condensation , to fit the small available volumes of the cell. In eukaryotes, DNA is located in the cell nucleus , with small amounts in mitochondria and chloroplasts . In prokaryotes, the DNA is held within an irregularly shaped body in

7072-550: The following Archaic Period . Researchers continue to study and discuss the specifics of Paleo-Indian migration to and throughout the Americas , including the dates and routes traveled. The traditional theory holds that these early migrants moved into Beringia between eastern Siberia and present-day Alaska 17,000 years ago, at a time when the Quaternary glaciation significantly lowered sea levels. These people are believed to have followed herds of now-extinct pleistocene megafauna along ice-free corridors that stretched between

7176-456: The forests and marshes. The fall would have been a busy time because foodstuffs would have to be stored and clothing made ready for the winter. During the winter, coastal fishing groups moved inland to hunt and trap fresh food and furs. Late ice-age climatic changes caused plant communities and animal populations to change. Groups moved and sought new supplies as preferred resources were depleted. Small bands utilized hunting and gathering during

7280-461: The four major types of macromolecules that are essential for all known forms of life . The two DNA strands are known as polynucleotides as they are composed of simpler monomeric units called nucleotides . Each nucleotide is composed of one of four nitrogen-containing nucleobases ( cytosine [C], guanine [G], adenine [A] or thymine [T]), a sugar called deoxyribose , and a phosphate group . The nucleotides are joined to one another in

7384-448: The functions of these RNAs are not entirely clear. One proposal is that antisense RNAs are involved in regulating gene expression through RNA-RNA base pairing. A few DNA sequences in prokaryotes and eukaryotes, and more in plasmids and viruses , blur the distinction between sense and antisense strands by having overlapping genes . In these cases, some DNA sequences do double duty, encoding one protein when read along one strand, and

7488-647: The grasslands include sotol, cholla, yucca, and Apache plume. Wildlife includes mountain lion, pronghorn, mule deer, black bear, and coyote as well as numerous bird species. Paleoindian Paleo-Indians were the first peoples who entered and subsequently inhabited the Americas towards the end of the Late Pleistocene period. The prefix paleo- comes from the Ancient Greek adjective: παλαιός , romanized :  palaiós , lit.   'old; ancient'. The term Paleo-Indians applies specifically to

7592-448: The helical axis in a left-handed spiral, the opposite of the more common B form. These unusual structures can be recognized by specific Z-DNA binding proteins and may be involved in the regulation of transcription. For many years, exobiologists have proposed the existence of a shadow biosphere , a postulated microbial biosphere of Earth that uses radically different biochemical and molecular processes than currently known life. One of

7696-448: The hydration level, DNA sequence, the amount and direction of supercoiling, chemical modifications of the bases, the type and concentration of metal ions , and the presence of polyamines in solution. The first published reports of A-DNA X-ray diffraction patterns —and also B-DNA—used analyses based on Patterson functions that provided only a limited amount of structural information for oriented fibers of DNA. An alternative analysis

7800-427: The hydrolytic activities of cellular water, etc., also occur frequently. Although most of these damages are repaired, in any cell some DNA damage may remain despite the action of repair processes. These remaining DNA damages accumulate with age in mammalian postmitotic tissues. This accumulation appears to be an important underlying cause of aging. Many mutagens fit into the space between two adjacent base pairs, this

7904-412: The importance of 5-methylcytosine, it can deaminate to leave a thymine base, so methylated cytosines are particularly prone to mutations . Other base modifications include adenine methylation in bacteria, the presence of 5-hydroxymethylcytosine in the brain , and the glycosylation of uracil to produce the "J-base" in kinetoplastids . DNA can be damaged by many sorts of mutagens , which change

8008-534: The individual groups shared a common style of stone tool production, making knapping styles and progress identifiable. This early Paleo-Indian period's lithic reduction tool adaptations have been found across the Americas, utilized by highly mobile bands consisting of approximately 20 to 60 members of an extended family. Food would have been plentiful during the few warm months of the year. Lakes and rivers were teeming with many species of fish, birds and aquatic mammals. Nuts, berries and edible roots could be found in

8112-510: The initial peopling of the Americas, and secondly with European colonization of the Americas . The former is the determinant factor for the number of gene lineages and founding haplotypes present in today's Indigenous Amerindian populations. Human settlement of the Americas occurred in stages from the Bering sea coast line , with an initial layover on Beringia for the founding population . The micro-satellite diversity and distributions of

8216-452: The migration time frame of ice-free corridors, thus suggesting that there were additional coastal migration routes available, traversed either on foot and/or in boats. Geological evidence suggests the Pacific coastal route was open for overland travel before 23,000 years ago and after 16,000 years ago. In South America, the site of Monte Verde indicates that its population was probably territorial and resided in their river basin for most of

8320-441: The minor groove is 12 Å (1.2 nm) in width. Due to the larger width of the major groove, the edges of the bases are more accessible in the major groove than in the minor groove. As a result, proteins such as transcription factors that can bind to specific sequences in double-stranded DNA usually make contact with the sides of the bases exposed in the major groove. This situation varies in unusual conformations of DNA within

8424-516: The mitochondrial genome (constituting up to 90% of the DNA of the cell). A DNA sequence is called a "sense" sequence if it is the same as that of a messenger RNA copy that is translated into protein. The sequence on the opposite strand is called the "antisense" sequence. Both sense and antisense sequences can exist on different parts of the same strand of DNA (i.e. both strands can contain both sense and antisense sequences). In both prokaryotes and eukaryotes, antisense RNA sequences are produced, but

8528-477: The most dangerous are double-strand breaks, as these are difficult to repair and can produce point mutations , insertions , deletions from the DNA sequence, and chromosomal translocations . These mutations can cause cancer . Because of inherent limits in the DNA repair mechanisms, if humans lived long enough, they would all eventually develop cancer. DNA damages that are naturally occurring , due to normal cellular processes that produce reactive oxygen species,

8632-493: The name big-game hunters . Pacific coastal groups of the period would have relied on fishing as the prime source of sustenance. Archaeologists are piecing together evidence that the earliest human settlements in North America were thousands of years before the appearance of the current Paleo-Indian time frame (before the late glacial maximum 20,000-plus years ago). Evidence indicates that people were living as far east as Beringia before 30,000 BCE (32,000 BP). Until recently, it

8736-464: The new strand, and the cell ends up with a perfect copy of its DNA. Naked extracellular DNA (eDNA), most of it released by cell death, is nearly ubiquitous in the environment. Its concentration in soil may be as high as 2 μg/L, and its concentration in natural aquatic environments may be as high at 88 μg/L. Various possible functions have been proposed for eDNA: it may be involved in horizontal gene transfer ; it may provide nutrients; and it may act as

8840-776: The now Magdalena Ranger District was a province of the Apache . Bands of Apache effectively controlled the Magdalena-Datil region from the seventeenth century until they were defeated in the Apache Wars in the late nineteenth century. Due to the absence of major light pollution, the Bear Mountains provide outstanding stargazing opportunities. The area also offers phenomenal hiking, backpacking, camping, hunting, and horseback-riding. As Robert Juylan points out in The Mountains of New Mexico ,

8944-454: The open reading frame. In many species , only a small fraction of the total sequence of the genome encodes protein. For example, only about 1.5% of the human genome consists of protein-coding exons , with over 50% of human DNA consisting of non-coding repetitive sequences . The reasons for the presence of so much noncoding DNA in eukaryotic genomes and the extraordinary differences in genome size , or C-value , among species, represent

9048-721: The passage of time there is a pattern of increasing regional generalization like the Southwest , Arctic , Poverty , Dalton , and Plano traditions. These regional adaptations would become the norm, with reliance less on hunting and gathering, and a more mixed economy of small game, fish, seasonally wild vegetables, and harvested plant foods. Many groups continued to hunt big game but their hunting traditions became more varied and meat procurement methods more sophisticated. The placement of artifacts and materials within an Archaic burial site indicated social differentiation based upon status in some groups. [REDACTED] Indigenous peoples of

9152-428: The place of thymine in RNA and differs from thymine by lacking a methyl group on its ring. In addition to RNA and DNA, many artificial nucleic acid analogues have been created to study the properties of nucleic acids, or for use in biotechnology. Modified bases occur in DNA. The first of these recognized was 5-methylcytosine , which was found in the genome of Mycobacterium tuberculosis in 1925. The reason for

9256-530: The presence of these noncanonical bases in bacterial viruses ( bacteriophages ) is to avoid the restriction enzymes present in bacteria. This enzyme system acts at least in part as a molecular immune system protecting bacteria from infection by viruses. Modifications of the bases cytosine and adenine, the more common and modified DNA bases, play vital roles in the epigenetic control of gene expression in plants and animals. A number of noncanonical bases are known to occur in DNA. Most of these are modifications of

9360-543: The primary evidence of the earliest human activity in the Americas. Archeologists and anthropologists use surviving crafted lithic flaked tools to classify cultural periods. Scientific evidence links Indigenous Americans to eastern Siberian populations by the distribution of blood types, and genetic composition as indicated by molecular data, such as DNA . There is evidence for at least two separate migrations. Paleoindians lived alongside and hunted many now extinct megafauna (large animals), with most large animals across

9464-412: The prime symbol being used to distinguish these carbon atoms from those of the base to which the deoxyribose forms a glycosidic bond . Therefore, any DNA strand normally has one end at which there is a phosphate group attached to the 5′ carbon of a ribose (the 5′ phosphoryl) and another end at which there is a free hydroxyl group attached to the 3′ carbon of a ribose (the 3′ hydroxyl). The orientation of

9568-466: The proposals was the existence of lifeforms that use arsenic instead of phosphorus in DNA . A report in 2010 of the possibility in the bacterium GFAJ-1 was announced, though the research was disputed, and evidence suggests the bacterium actively prevents the incorporation of arsenic into the DNA backbone and other biomolecules. At the ends of the linear chromosomes are specialized regions of DNA called telomeres . The main function of these regions

9672-451: The range is rather popular among birdwatchers because of the various springs in the region. As with other mountain ranges in west-central New Mexico, the variations in elevation result in diverse vegetative types. Scrubland, pinyon-juniper woodland, Gambel oak, mountain mahogany and grassland areas are all represented. Grasses include black and sideoats grama, poverty threeawn, fluffgrass, burrograss, and galleta grass. Shrubs that are mixed in

9776-432: The section on uses in technology below. Several artificial nucleobases have been synthesized, and successfully incorporated in the eight-base DNA analogue named Hachimoji DNA . Dubbed S, B, P, and Z, these artificial bases are capable of bonding with each other in a predictable way (S–B and P–Z), maintain the double helix structure of DNA, and be transcribed to RNA. Their existence could be seen as an indication that there

9880-431: The sequence of amino acids within proteins in a process called translation . Within eukaryotic cells, DNA is organized into long structures called chromosomes . Before typical cell division , these chromosomes are duplicated in the process of DNA replication, providing a complete set of chromosomes for each daughter cell. Eukaryotic organisms ( animals , plants , fungi and protists ) store most of their DNA inside

9984-473: The shape of a double helix . The nucleotide contains both a segment of the backbone of the molecule (which holds the chain together) and a nucleobase (which interacts with the other DNA strand in the helix). A nucleobase linked to a sugar is called a nucleoside , and a base linked to a sugar and to one or more phosphate groups is called a nucleotide . A biopolymer comprising multiple linked nucleotides (as in DNA)

10088-552: The single-ringed pyrimidines and the double-ringed purines . In DNA, the pyrimidines are thymine and cytosine; the purines are adenine and guanine. Both strands of double-stranded DNA store the same biological information . This information is replicated when the two strands separate. A large part of DNA (more than 98% for humans) is non-coding , meaning that these sections do not serve as patterns for protein sequences . The two strands of DNA run in opposite directions to each other and are thus antiparallel . Attached to each sugar

10192-498: The single-stranded DNA curls around in a long circle stabilized by telomere-binding proteins. At the very end of the T-loop, the single-stranded telomere DNA is held onto a region of double-stranded DNA by the telomere strand disrupting the double-helical DNA and base pairing to one of the two strands. This triple-stranded structure is called a displacement loop or D-loop . In DNA, fraying occurs when non-complementary regions exist at

10296-531: The spring and summer months, then broke into smaller direct family groups for the fall and winter. Family groups moved every 3–6 days, possibly traveling up to 360 km (220 mi) per year. Diets were often sustaining and rich in protein; clothing was made from a variety of animal hides that were also used for shelter construction. During much of the early and middle Paleo-Indian periods, inland bands are thought to have subsisted primarily through hunting now-extinct megafauna . Large Pleistocene mammals included

10400-518: The strands separate and exist in solution as two entirely independent molecules. These single-stranded DNA molecules have no single common shape, but some conformations are more stable than others. In humans, the total female diploid nuclear genome per cell extends for 6.37 Gigabase pairs (Gbp), is 208.23 cm long and weighs 6.51 picograms (pg). Male values are 6.27 Gbp, 205.00 cm, 6.41 pg. Each DNA polymer can contain hundreds of millions of nucleotides, such as in chromosome 1 . Chromosome 1

10504-469: The sugar-phosphate to form the complete nucleotide, as shown for adenosine monophosphate . Adenine pairs with thymine and guanine pairs with cytosine, forming A-T and G-C base pairs . The nucleobases are classified into two types: the purines , A and G , which are fused five- and six-membered heterocyclic compounds , and the pyrimidines , the six-membered rings C and T . A fifth pyrimidine nucleobase, uracil ( U ), usually takes

10608-796: The year. Some other South American groups, on the other hand, were highly mobile and hunted big-game animals such as gomphotheres and giant sloths . They used classic bifacial projectile point technology, such as Fishtail points . The primary examples are populations associated with El Jobo points ( Venezuela ), fish-tail or Magallanes points (various parts of the continent, but mainly the southern half), and Paijan points ( Peru and Ecuador ) at sites in grasslands, savanna plains, and patchy forests. The dating for these sites ranges from c.  14,000 BP (for Taima-Taima in Venezuela) to c.  10,000 BP. The bi-pointed El Jobo projectile points were mostly distributed in north-western Venezuela; from

10712-421: Was generally believed that the first Paleo-Indian people to arrive in North America belonged to the Clovis culture. This archaeological phase was named after the city of Clovis, New Mexico , where in 1936 unique Clovis points were found in situ at the site of Blackwater Draw , where they were directly associated with the bones of Pleistocene animals. Recent data from a series of archaeological sites throughout

10816-517: Was proposed by Wilkins et al. in 1953 for the in vivo B-DNA X-ray diffraction-scattering patterns of highly hydrated DNA fibers in terms of squares of Bessel functions . In the same journal, James Watson and Francis Crick presented their molecular modeling analysis of the DNA X-ray diffraction patterns to suggest that the structure was a double helix. Although the B-DNA form is most common under

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