The list of organisms by chromosome count describes ploidy or numbers of chromosomes in the cells of various plants, animals, protists, and other living organisms. This number, along with the visual appearance of the chromosome, is known as the karyotype, [1] [2] [3] and can be found by looking at the chromosomes through a microscope. Attention is paid to their length, the position of the centromeres, banding pattern, any differences between the sex chromosomes, and any other physical characteristics. [4] The preparation and study of karyotypes is part of cytogenetics.
S. No. | Organism (B SULLAR) | Chromosome number | Picture | Karyotype | Notes | Source |
---|---|---|---|---|---|---|
1 | Jack jumper ant (Myrmecia pilosula) | 2/1 | 2 for females, males are haploid and thus have 1; smallest number possible. Other ant species have more chromosomes. [5] | [5] | ||
2 | Spider mite (Tetranychidae) | 4–14 | Spider mites (family Tetranychidae) are typically haplodiploid (males are haploid, while females are diploid) [6] | [6] | ||
3 | Cricotopus sylvestris | 4 | [7] | |||
4 | Oikopleura dioica | 6 | [8] | |||
5 | Yellow fever mosquito (Aedes aegypti) | 6 | The 2n=6 chromosome number is conserved in the entire family Culicidae, except in Chagasia bathana , which has 2n=8. [9] | [9] | ||
6 | Indian muntjac (Muntiacus muntjak) | 6/7 | 2n = 6 for females and 7 for males. The lowest diploid chromosomal number in mammals. [10] | [11] | ||
7 | Hieracium | 8 | ||||
8 | Fruit fly ( Drosophila melanogaster ) | 8 | 6 autosomal and 2 allosomic (sex) | [12] | ||
9 | Macrostomum lignano | 8 | [13] | |||
10 | Marchantia polymorpha | 9 | Typically haploid with dominant gametophyte stage. 8 autosomes and 1 allosome (sex chromosome). The sex-determination system used by this species and most other bryophytes is called UV. Spores can carry either the U chromosome, which results in female gametophytes, or the V chromosome, which results in males. The chromosome number n = 9 is the basic number in many species of Marchantiales. In some species of Marchantiales, plants with various ploidy levels (having 18 or 27 chromosomes) were reported, but this is rare in nature. | [14] | ||
11 | Thale cress (Arabidopsis thaliana) | 10 | ||||
12 | Swamp wallaby (Wallabia bicolor) | 10/11 | 11 for male, 10 for female | [15] | ||
13 | Australian daisy ( Brachyscome dichromosomatica) | 12 | This species can have more B chromosomes than A chromosomes at times, but 2n=4. | [16] | ||
14 | Nematode ( Caenorhabditis elegans ) | 12/11 | 12 for hermaphrodites, 11 for males | |||
15 | Spinach (Spinacia oleracea) | 12 | [17] | |||
16 | Broad bean (Vicia faba) | 12 | [18] | |||
17 | Yellow dung fly (Scathophaga stercoraria) | 12 | 10 autosomal and 2 allosomic (sex) chromosomes. Males have XY sex chromosomes and females have XX sex chromosomes. The sex chromosomes are the largest chromosomes and constitute 30% of the total length of the diploid set in females and about 25% in males. [19] | [19] | ||
18 | Slime mold ( Dictyostelium discoideum ) | 12 | [20] | |||
19 | Cucumber (Cucumis sativus) | 14 | [21] | |||
20 | Tasmanian devil (Sarcophilus harrisii) | 14 | ||||
21 | Rye (Secale cereale) | 14 | [22] | |||
22 | Pea (Pisum sativum) | 14 | [22] | |||
23 | Barley (Hordeum vulgare) | 14 | [23] | |||
24 | Aloe vera | 14 | The diploid chromosome number is 2n = 14 with four pair of long acrocentric chromosomes ranging from 14.4 μm to 17.9 μm and three pair of short sub metacentric chromosomes ranging from 4.6 μm to 5.4 μm. [24] | [24] | ||
25 | Koala (Phascolarctos cinereus) | 16 | ||||
26 | Kangaroo | 16 | This includes several members of genus Macropus , but not the red kangaroo (M. rufus, 20) | [25] | ||
27 | Botryllus schlosseri | 16 | [26] | |||
28 | Schistosoma mansoni | 16 | 2n=16. 7 autosomal pairs and ZW sex-determination pair. [27] | [27] | ||
29 | Welsh onion (Allium fistulosum) | 16 | [28] | |||
30 | Garlic (Allium sativum) | 16 | [28] | |||
31 | Itch mite (Sarcoptes scabiei) | 17/18 | According to the observation of embryonic cells of egg, chromosome number of the itch mite is either 17 or 18. While the cause for the disparate numbers is unknown, it may arise because of an XO sex determination mechanism, where males (2n=17) lack the sex chromosome and therefore have one less chromosome than the female (2n=18). [29] | [29] | ||
32 | Radish (Raphanus sativus) | 18 | [22] | |||
33 | Carrot ( Daucus carota ) | 18 | The genus Daucus includes around 25 species. D. carota has nine chromosome pairs (2n = 2x = 18). D. capillifolius, D. sahariensis and D. syrticus are the other members of the genus with 2n = 18, whereas D. muricatus (2n = 20) and D. pusillus (2n = 22) have a slightly higher chromosome number. A few polyploid species as for example D. glochidiatus (2n = 4x = 44) and D. montanus (2n = 6x = 66) also exist. [30] | [30] | ||
34 | Cabbage (Brassica oleracea) | 18 | Broccoli, cabbage, kale, kohlrabi, brussels sprouts, and cauliflower are all the same species and have the same chromosome number. [22] | [22] | ||
35 | Citrus (Citrus) | 18 | Chromosome number of the genus Citrus , which including lemons, oranges, grapefruit, pomelo and limes, is 2n = 18. [31] | [32] | ||
36 | Passion fruit (Passiflora edulis) | 18 | [33] | |||
37 | Setaria viridis (Setaria viridis) | 18 | [34] | |||
38 | Maize (Zea mays) | 20 | [22] | |||
39 | Cannabis ( Cannabis sativa ) | 20 | ||||
40 | Western clawed frog (Xenopus tropicalis) | 20 | [35] | |||
41 | Australian pitcher plant (Cephalotus follicularis) | 20 | [36] | |||
42 | Cacao (Theobroma cacao) | 20 | [37] | |||
43 | Eucalyptus (Eucalyptus) | 22 | Although some contradictory cases have been reported, the large homogeneity of the chromosome number 2n = 22 is now known for 135 (33.5%) distinct species among genus Eucalyptus . [38] | [39] | ||
44 | Virginia opossum (Didelphis virginiana) | 22 | [40] | |||
45 | Bean (Phaseolus sp.) | 22 | All species in the genus Phaseolus have the same chromosome number, including common bean (P. vulgaris), runner bean (P. coccineus), tepary bean (P. acutifolius) and lima bean (P. lunatus). [22] | [22] | ||
46 | Snail | 24 | ||||
47 | Melon (Cucumis melo) | 24 | [41] | |||
48 | Rice (Oryza sativa) | 24 | [22] | |||
49 | Silverleaf nightshade (Solanum elaeagnifolium) | 24 | [42] | |||
50 | Sweet chestnut (Castanea sativa) | 24 | [43] | |||
51 | Tomato (Solanum lycopersicum) | 24 | [44] | |||
52 | European beech (Fagus sylvatica) | 24 | [45] | |||
53 | Bittersweet nightshade (Solanum dulcamara) | 24 | [46] [47] | |||
54 | Cork oak (Quercus suber) | 24 | [48] | |||
55 | Edible frog (Pelophylax kl. esculentus) | 26 | Edible frog is the fertile hybrid of the pool frog and the marsh frog. [49] | [50] | ||
56 | Axolotl (Ambystoma mexicanum) | 28 | [51] | |||
57 | Bed bug (Cimex lectularius) | 29–47 | 26 autosomes and varying number of the sex chromosomes from three (X1X2Y) to 21 (X1X2Y+18 extra Xs). [52] | [52] | ||
58 | Pill millipede (Arthrosphaera magna attems) | 30 | [53] | |||
59 | Giraffe (Giraffa camelopardalis) | 30 | [54] | |||
60 | American mink (Neogale vison) | 30 | ||||
61 | Pistachio (Pistacia vera) | 30 | [55] | |||
62 | Japanese oak silkmoth (Antheraea yamamai) | 31 | [56] | |||
63 | Baker's yeast (Saccharomyces cerevisiae) | 32 | ||||
64 | European honey bee (Apis mellifera) | 32/16 | 32 for females (2n = 32), males are haploid and thus have 16 (1n =16). [57] | [57] | ||
65 | American badger (Taxidea taxus) | 32 | ||||
66 | Alfalfa (Medicago sativa) | 32 | Cultivated alfalfa is tetraploid, with 2n=4x=32. Wild relatives have 2n=16. [22] : 165 | [22] | ||
67 | Red fox (Vulpes vulpes) | 34 | Plus 0-8 B chromosomes. | [58] | ||
68 | Sunflower (Helianthus annuus) | 34 | [59] | |||
69 | Porcupine (Erethizon dorsatum) | 34 | [60] | |||
70 | Globe artichoke (Cynara cardunculus var. scolymus) | 34 | [61] | |||
71 | Yellow mongoose (Cynictis penicillata) | 36 | ||||
72 | Tibetan sand fox (Vulpes ferrilata) | 36 | ||||
73 | Starfish (Asteroidea) | 36 | ||||
74 | Red panda (Ailurus fulgens) | 36 | ||||
75 | Meerkat (Suricata suricatta) | 36 | ||||
76 | Cassava (Manihot esculenta) | 36 | [62] | |||
77 | Long-nosed cusimanse (Crossarchus obscurus) | 36 | ||||
78 | Earthworm (Lumbricus terrestris) | 36 | ||||
79 | African clawed frog (Xenopus laevis) | 36 | [35] | |||
80 | Waterwheel plant (Aldrovanda vesiculosa) | 38 | [36] | |||
81 | Tiger (Panthera tigris) | 38 | ||||
82 | Sea otter (Enhydra lutris) | 38 | ||||
83 | Sable (Martes zibellina) | 38 | ||||
84 | Raccoon (Procyon lotor) | 38 | [63] | |||
85 | Pine marten (Martes martes) | 38 | ||||
86 | Pig (Sus) | 38 | ||||
87 | Oriental small-clawed otter (Aonyx cinerea) | 38 | ||||
88 | Lion (Panthera leo) | 38 | ||||
89 | Fisher (Pekania pennanti) | 38 | a type of marten | |||
90 | European mink (Mustela lutreola) | 38 | ||||
91 | Coatimundi | 38 | ||||
92 | Cat (Felis catus) | 38 | ||||
93 | Beech marten (Martes foina) | 38 | ||||
94 | Baja California rat snake (Bogertophis rosaliae) | 38 | [64] | |||
95 | American marten (Martes americana) | 38 | ||||
96 | Trans-Pecos ratsnake (Bogertophis subocularis) | 40 | [65] | |||
97 | Mouse (Mus musculus) | 40 | [66] | |||
98 | Mango (Mangifera indica) | 40 | [22] | |||
99 | Hyena (Hyaenidae) | 40 | ||||
100 | Ferret (Mustela furo) | 40 | ||||
101 | European polecat (Mustela putorius) | 40 | ||||
102 | American beaver (Castor canadensis) | 40 | ||||
103 | Peanut (Arachis hypogaea) | 40 | Cultivated peanut is an allotetraploid (2n = 4x = 40). Its closest relatives are the diploid (2n = 2x = 20). [67] | [67] | ||
104 | Wolverine (Gulo gulo) | 42 | ||||
105 | Wheat (Triticum aestivum) | 42 | This is a hexaploid with 2n=6x=42. Durum wheat is Triticum turgidum var. durum, and is a tetraploid with 2n=4x=28. [22] | [22] | ||
106 | Rhesus monkey (Macaca mulatta) | 42 | [68] | |||
107 | Rat (Rattus norvegicus) | 42 | [69] | |||
108 | Oats (Avena sativa) | 42 | This is a hexaploid with 2n=6x=42. Diploid and tetraploid cultivated species also exist. [22] | [22] | ||
109 | Giant panda (Ailuropoda melanoleuca) | 42 | ||||
110 | Fossa (Cryptoprocta ferox) | 42 | ||||
111 | European rabbit (Oryctolagus cuniculus) | 44 | ||||
112 | Eurasian badger (Meles meles) | 44 | ||||
113 | Moon jellyfish (Aurelia aurita) | 44 | [70] | |||
114 | Dolphin (Delphinidae) | 44 | ||||
115 | Arabian coffee (Coffea arabica) | 44 | Out of the 103 species in the genus Coffea , arabica coffee is the only tetraploid species (2n = 4x = 44), the remaining species being diploid with 2n = 2x = 22. [71] | |||
116 | Reeves's muntjac (Muntiacus reevesi) | 46 | ||||
117 | Human (Homo sapiens) | 46 | 44 autosomal. and 2 allosomic (sex) | [72] | ||
118 | Olive (Olea Europaea) | 46 | ||||
119 | Nilgai (Boselaphus tragocamelus) | 46 | [73] | |||
120 | Parhyale hawaiensis | 46 | [74] | |||
121 | Water buffalo (swamp type) (Bubalus bubalis) | 48 | ||||
122 | Tobacco ( Nicotiana tabacum ) | 48 | Cultivated species N. tabacum is an amphidiploid (2n=4x=48) evolved through the interspecific hybridization of the ancestors of N. sylvestris (2n=2x=24, maternal donor) and N. tomentosiformis (2n=2x=24, paternal donor) about 200,000 years ago. [75] | [75] | ||
123 | Potato (Solanum tuberosum) | 48 | This is for common potato Solanum tuberosum (tetraploid, 2n = 4x = 48). Other cultivated potato species may be diploid (2n = 2x = 24), triploid (2n = 3x = 36), tetraploid (2n = 4x = 48), or pentaploid (2n = 5x = 60). [76] Wild relatives mostly have 2n=24. [22] | [76] | ||
124 | Orangutan (Pongo) | 48 | ||||
125 | Hare (Lepus) | 48 | [77] [78] | |||
126 | Gorilla (Gorilla) | 48 | ||||
127 | Deer mouse (Peromyscus maniculatus) | 48 | ||||
128 | Chimpanzee (Pan troglodytes) | 48 | [79] | |||
129 | Eurasian beaver (Castor fiber) | 48 | ||||
130 | Zebrafish (Danio rerio) | 50 | [80] | |||
131 | Woodland hedgehogs Erinaceus | 48 | [81] | |||
132 | African hedgehogs Atelerix | 48 | [82] | |||
133 | Water buffalo (Riverine type) (Bubalus bubalis) | 50 | ||||
134 | Striped skunk (Mephitis mephitis) | 50 | ||||
135 | Pineapple (Ananas comosus) | 50 | [22] | |||
136 | Kit fox (Vulpes macrotis) | 50 | ||||
137 | Spectacled bear (Tremarctos ornatus) | 52 | ||||
138 | Platypus (Ornithorhynchus anatinus) | 52 | Ten sex chromosomes. Males have X1Y1X2Y2X3Y3X4Y4X5Y5, females have X1X1X2X2X3X3X4X4X5X5. [83] | [84] | ||
139 | Upland cotton (Gossypium hirsutum) | 52 | This is for the cultivated species G. hirsutum (allotetraploid, 2n=4x=52). This species accounts for 90% of the world cotton production. Among 50 species in the genus Gossypium , 45 are diploid (2n = 2x = 26) and 5 are allotetraploid (2n = 4x = 52). [85] | [85] | ||
140 | Sheep (Ovis aries) | 54 | ||||
141 | Hyrax (Hyracoidea) | 54 | Hyraxes were considered to be the closest living relatives of elephants, [86] but sirenians have been found to be more closely related to elephants. | [87] | ||
142 | Raccoon dog (Nyctereutes procyonoides procyonoides) | 54 | This number is for common raccoon dog (N. p. procyonoides), 2n=54+B(0–4). On the other hand, Japanese raccoon dog (N. p. viverrinus) with 2n=38+B(0–8). Here, B represents B chromosome and its variation in the number between individuals. [88] [89] | [88] | ||
143 | Capuchin monkey (Cebinae) | 54 | [90] | |||
144 | Silkworm (Bombyx mori) | 56 | This is for the species mulberry silkworm, B. mori (2n=56). Probably more than 99% of the world's commercial silk today come from this species. [91] Other silk producing moths, called non-mulberry silkworms, have various chromosome numbers. (e.g. Samia cynthia with 2n=25–28, [92] Antheraea pernyi with 2n=98. [93] ) | [94] | ||
145 | Strawberry (Fragaria × ananassa) | 56 | This number is octoploid, main cultivated species Fragaria × ananassa (2n = 8x = 56). In genus Fragaria , basic chromosome number is seven (x = 7) and multiple levels of ploidy, ranging from diploid (2n = 2x = 14) to decaploid ( F. iturupensis , 2n = 10x = 70), are known. [95] | [95] | ||
146 | Gaur (Bos gaurus) | 56 | ||||
147 | Elephant (Elephantidae) | 56 | ||||
148 | †Woolly mammoth (Mammuthus primigenius) | 58 | extinct; tissue from a frozen carcass | |||
149 | Domestic yak (Bos grunniens) | 60 | ||||
150 | Goat (Capra hircus) | 60 | ||||
151 | Cattle (Bos taurus) | 60 | ||||
152 | American bison (Bison bison) | 60 | ||||
153 | Sable antelope (Hippotragus niger) | 60 | [96] | |||
154 | Bengal fox (Vulpes bengalensis) | 60 | ||||
155 | Gypsy moth (Lymantria dispar dispar) | 62 | ||||
156 | Donkey (Equus asinus) | 62 | ||||
157 | Scarlet macaw (Ara macao) | 62–64 | [97] | |||
158 | Mule | 63 | semi-infertile (odd number of chromosomes – between donkey (62) and horse (64) makes meiosis much more difficult) | |||
159 | Guinea pig (Cavia porcellus) | 64 | ||||
160 | Spotted skunk (Spilogale x) | 64 | ||||
161 | Horse (Equus caballus) | 64 | ||||
162 | Fennec fox (Vulpes zerda) | 64 | [98] | |||
163 | Echidna (Tachyglossidae) | 63/64 | 63 (X1Y1X2Y2X3Y3X4Y4X5, male) and 64 (X1X1X2X2X3X3X4X4X5X5, female) [99] | |||
164 | Chinchilla (Chinchilla lanigera) | 64 | [60] | |||
165 | Nine-banded armadillo (Dasypus novemcinctus) | 64 | [100] | |||
166 | Gray fox (Urocyon cinereoargenteus) | 66 | [98] | |||
167 | Red deer (Cervus elaphus) | 68 | ||||
168 | Elk (wapiti) (Cervus canadensis) | 68 | ||||
169 | Roadside hawk (Rupornis magnirostris) | 68 | [101] | |||
170 | White-tailed deer (Odocoileus virginianus) | 70 | ||||
171 | Black nightshade ( Solanum nigrum ) | 72 | [102] | |||
172 | Tropical blue bamboo ( Bambusa chungii ) | 64–72 | [103] | |||
173 | Bat-eared fox (Otocyon megalotis) | 72 | [98] | |||
174 | Sun bear (Helarctos malayanus) | 74 | ||||
175 | Sloth bear (Melursus ursinus) | 74 | ||||
176 | Polar bear (Ursus maritimus) | 74 | ||||
177 | Brown bear (Ursus arctos) | 74 | ||||
178 | Asian black bear (Ursus thibetanus) | 74 | ||||
179 | American black bear (Ursus americanus) | 74 | ||||
180 | Bush dog (Speothos venaticus) | 74 | ||||
181 | Maned wolf (Chrysocyon brachyurus) | 76 | ||||
182 | Gray wolf (Canis lupus) | 78 | ||||
183 | Golden jackal (Canis aureus) | 78 | [98] | |||
184 | Dove (Columbidae) | 78 | Based on African collared dove | [104] | ||
185 | Dog (Canis familiaris) | 78 | Normal dog karyotype is composed of 38 pairs of acrocentric autosomes and two metacentric sex chromosomes. [105] [106] | [107] | ||
186 | Dingo (Canis familiaris) | 78 | [98] | |||
187 | Dhole (Cuon alpinus) | 78 | ||||
188 | Coyote (Canis latrans) | 78 | [98] | |||
189 | Chicken (Gallus gallus domesticus) | 78 | ||||
190 | African wild dog (Lycaon pictus) | 78 | [98] | |||
191 | Tropical pitcher plant (Nepenthes rafflesiana) | 78 | [36] | |||
192 | Turkey (Meleagris) | 80 | [108] | |||
193 | Sugarcane ( Saccharum officinarum ) | 80 | This is for S. officinarum (octoploid, 2n = 8× = 80). [109] About 70% of the world's sugar comes from this species. [110] Other species in the genus Saccharum , collectively known as sugarcane, have chromosome numbers in the range 2n=40–128. [111] | [109] | ||
194 | Pigeon (Columbidae) | 80 | [112] | |||
195 | Azure-winged magpie (Cyanopica cyanus) | 80 | [113] | |||
196 | Great white shark (Carcharodon carcharias) | 82 | [114] | |||
197 | Bloody geranium (Geranium sanguineum) | 84 | [115] | |||
198 | Moonworts (Botrychium) | 90 | ||||
199 | Grape fern (Sceptridium) | 90 | ||||
200 | Pittier's crab-eating rat (Ichthyomys pittieri) | 92 | Previously thought to be the highest number in mammals, tied with Anotomys leander. | [116] | ||
201 | Prawn ( Penaeus semisulcatus ) | 86–92 | [117] | |||
202 | Aquatic rat (Anotomys leander) | 92 | Previously thought to be the highest number in mammals, tied with Ichthyomys pittieri. | [116] | ||
203 | Kamraj (fern) (Helminthostachys zeylanica) | 94 | ||||
204 | Crucian carp (Carassius carassius) | 100 | [118] | |||
205 | Red viscacha rat (Tympanoctomys barrerae) | 102 | Highest number known in mammals, thought to be a tetraploid [119] or allotetraploid. [120] | [121] | ||
206 | Walking catfish (Clarias batrachus) | 104 | [122] | |||
207 | American paddlefish (Polyodon spathula) | 120 | [123] | |||
208 | Limestone fern (Gymnocarpium robertianum) | 160 | Tetraploid (2n = 4x = 160) | [124] | ||
209 | African baobab (Adansonia digitata) | 168 | Also known as the "tree of life". 2n = 4x = 168 | [125] | ||
210 | Northern lampreys (Petromyzontidae) | 174 | [126] | |||
211 | Rattlesnake fern (Botrypus virginianus) | 184 | [127] | |||
212 | Red king crab (Paralithodes camtschaticus) | 208 | ||||
213 | Field horsetail (Equisetum arvense) | 216 | ||||
214 | Agrodiaetus butterfly (Agrodiaetus shahrami) | 268 | This insect has one of the highest chromosome numbers among all animals. | [128] | ||
215 | Black mulberry (Morus nigra) | 308 | Highest ploidy among plants, 22-ploid (2n = 22x = 308) [129] | [130] | ||
216 | Atlas blue (Polyommatus atlantica) | 448–452 | 2n = c. 448–452. Highest number of chromosomes in the non-polyploid eukaryotic organisms. [131] | [131] | ||
217 | Adders-tongue ( Ophioglossum reticulatum ) | 1260 | n=120–720 with a high degree of polyploidization. [132] Ophioglossum reticulatum n=720 in hexaploid species, 2n=1260 in decaploid species. [133] | |||
218 | Ciliated protozoa ( Tetrahymena thermophila ) | 10 (in micronucleus) | 50x = 12,500 (in macronucleus, except minichromosomes) 10,000x = 10,000 (macronuclear minichromosomes) [134] | |||
219 | Ciliated protozoa ( Sterkiella histriomuscorum ) | 16,000 [135] | Macronuclear "nanochromosomes"; ampliploid. MAC chromosomes × 1900 ploidy level = 2.964 × 107 chromosomes | [136] [137] [138] |
In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA. The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as regulatory sequences, and often a substantial fraction of junk DNA with no evident function. Almost all eukaryotes have mitochondria and a small mitochondrial genome. Algae and plants also contain chloroplasts with a chloroplast genome.
Polyploidy is a condition in which the cells of an organism have more than one pair of (homologous) chromosomes. Most species whose cells have nuclei (eukaryotes) are diploid, meaning they have two complete sets of chromosomes, one from each of two parents; each set contains the same number of chromosomes, and the chromosomes are joined in pairs of homologous chromosomes. However, some organisms are polyploid. Polyploidy is especially common in plants. Most eukaryotes have diploid somatic cells, but produce haploid gametes by meiosis. A monoploid has only one set of chromosomes, and the term is usually only applied to cells or organisms that are normally diploid. Males of bees and other Hymenoptera, for example, are monoploid. Unlike animals, plants and multicellular algae have life cycles with two alternating multicellular generations. The gametophyte generation is haploid, and produces gametes by mitosis; the sporophyte generation is diploid and produces spores by meiosis.
The Y chromosome is one of two sex chromosomes in therian mammals and other organisms. Along with the X chromosome, it is part of the XY sex-determination system, in which the Y is the sex-determining because it is the presence or absence of Y chromosome that determines the male or female sex of offspring produced in sexual reproduction. In mammals, the Y chromosome contains the SRY gene, which triggers development of male gonads. The Y chromosome is passed only from male parents to male offspring.
Afrotheria is a superorder of mammals, the living members of which belong to groups that are either currently living in Africa or of African origin: golden moles, elephant shrews, otter shrews, tenrecs, aardvarks, hyraxes, elephants, sea cows, and several extinct clades. Most groups of afrotheres share little or no superficial resemblance, and their similarities have only become known in recent times because of genetics and molecular studies. Many afrothere groups are found mostly or exclusively in Africa, reflecting the fact that Africa was an island continent from the Cretaceous until the early Miocene around 20 million years ago, when Afro-Arabia collided with Eurasia.
Comparative genomics is a field of biological research in which the genomic features of different organisms are compared. The genomic features may include the DNA sequence, genes, gene order, regulatory sequences, and other genomic structural landmarks. In this branch of genomics, whole or large parts of genomes resulting from genome projects are compared to study basic biological similarities and differences as well as evolutionary relationships between organisms. The major principle of comparative genomics is that common features of two organisms will often be encoded within the DNA that is evolutionarily conserved between them. Therefore, comparative genomic approaches start with making some form of alignment of genome sequences and looking for orthologous sequences in the aligned genomes and checking to what extent those sequences are conserved. Based on these, genome and molecular evolution are inferred and this may in turn be put in the context of, for example, phenotypic evolution or population genetics.
An inversion is a chromosome rearrangement in which a segment of a chromosome becomes inverted within its original position. An inversion occurs when a chromosome undergoes a two breaks within the chromosomal arm, and the segment between the two breaks inserts itself in the opposite direction in the same chromosome arm. The breakpoints of inversions often happen in regions of repetitive nucleotides, and the regions may be reused in other inversions. Chromosomal segments in inversions can be as small as 1 kilobases or as large as 100 megabases. The number of genes captured by an inversion can range from a handful of genes to hundreds of genes. Inversions can happen either through ectopic recombination between repetitive sequences, or through chromosomal breakage followed by non-homologous end joining.
Sequence homology is the biological homology between DNA, RNA, or protein sequences, defined in terms of shared ancestry in the evolutionary history of life. Two segments of DNA can have shared ancestry because of three phenomena: either a speciation event (orthologs), or a duplication event (paralogs), or else a horizontal gene transfer event (xenologs).
Molecular cytogenetics combines two disciplines, molecular biology and cytogenetics, and involves the analysis of chromosome structure to help distinguish normal and cancer-causing cells. Human cytogenetics began in 1956 when it was discovered that normal human cells contain 46 chromosomes. However, the first microscopic observations of chromosomes were reported by Arnold, Flemming, and Hansemann in the late 1800s. Their work was ignored for decades until the actual chromosome number in humans was discovered as 46. In 1879, Arnold examined sarcoma and carcinoma cells having very large nuclei. Today, the study of molecular cytogenetics can be useful in diagnosing and treating various malignancies such as hematological malignancies, brain tumors, and other precursors of cancer. The field is overall focused on studying the evolution of chromosomes, more specifically the number, structure, function, and origin of chromosome abnormalities. It includes a series of techniques referred to as fluorescence in situ hybridization, or FISH, in which DNA probes are labeled with different colored fluorescent tags to visualize one or more specific regions of the genome. Introduced in the 1980s, FISH uses probes with complementary base sequences to locate the presence or absence of the specific DNA regions. FISH can either be performed as a direct approach to metaphase chromosomes or interphase nuclei. Alternatively, an indirect approach can be taken in which the entire genome can be assessed for copy number changes using virtual karyotyping. Virtual karyotypes are generated from arrays made of thousands to millions of probes, and computational tools are used to recreate the genome in silico.
In human mitochondrial genetics, Haplogroup G is a human mitochondrial DNA (mtDNA) haplogroup.
Saccharomyces bayanus is a yeast of the genus Saccharomyces, and is used in winemaking and cider fermentation, and to make distilled beverages. Saccharomyces bayanus, like Saccharomyces pastorianus, is now accepted to be the result of multiple hybridisation events between three pure species, Saccharomyces uvarum, Saccharomyces cerevisiae and Saccharomyces eubayanus. Notably, most commercial yeast cultures sold as pure S. bayanus for wine making, e.g. Lalvin EC-1118 strain, have been found to contain S. cerevisiae cultures instead
Population genomics is the large-scale comparison of DNA sequences of populations. Population genomics is a neologism that is associated with population genetics. Population genomics studies genome-wide effects to improve our understanding of microevolution so that we may learn the phylogenetic history and demography of a population.
TOX high mobility group box family member 3, also known as TOX3, is a human gene.
Virtual karyotype is the digital information reflecting a karyotype, resulting from the analysis of short sequences of DNA from specific loci all over the genome, which are isolated and enumerated. It detects genomic copy number variations at a higher resolution for level than conventional karyotyping or chromosome-based comparative genomic hybridization (CGH). The main methods used for creating virtual karyotypes are array-comparative genomic hybridization and SNP arrays.
A microchromosome is a chromosome defined for its relatively small size. They are typical components of the karyotype of birds, some reptiles, fish, amphibians, and monotremes. As many bird genomes have chromosomes of widely different lengths, the name was meant to distinguish them from the comparatively large macrochromosomes. The distinction referred to the measured size of the chromosome while staining for karyotype, and while there is not a strict definition, chromosomes resembling the large chromosomes of mammals were called macrochromosomes, while the much smaller ones of less than around 0.5 µm were called microchromosomes. In terms of base pairs, by convention, those of less than 20Mb were called microchromosomes, those between 20 and 40 Mb are classified as intermediate chromosomes, and those larger than 40Mb are macrochromosomes. By this definition, all normal chromosomes in organisms with relatively small genomes would be considered microchromosomes.
The 2000s witnessed an explosion of genome sequencing and mapping in evolutionarily diverse species. While full genome sequencing of mammals is rapidly progressing, the ability to assemble and align orthologous whole chromosomal regions from more than a few species is not yet possible. The intense focus on the building of comparative maps for domestic, laboratory and agricultural (cattle) animals has traditionally been used to understand the underlying basis of disease-related and healthy phenotypes.
Holocentric chromosomes are chromosomes that possess multiple kinetochores along their length rather than the single centromere typical of other chromosomes. They were first described in cytogenetic experiments in 1935. Since this first observation, the term holocentric chromosome has referred to chromosomes that: i) lack the primary constriction corresponding to the centromere observed in monocentric chromosomes; and ii) possess multiple kinetochores dispersed along the entire chromosomal axis, such that microtubules bind to the chromosome along its entire length and move broadside to the pole from the metaphase plate. Holocentric chromosomes are also termed holokinetic, because, during cell division, the sister chromatids move apart in parallel and do not form the classical V-shaped figures typical of monocentric chromosomes.
Eukaryote hybrid genomes result from interspecific hybridization, where closely related species mate and produce offspring with admixed genomes. The advent of large-scale genomic sequencing has shown that hybridization is common, and that it may represent an important source of novel variation. Although most interspecific hybrids are sterile or less fit than their parents, some may survive and reproduce, enabling the transfer of adaptive variants across the species boundary, and even result in the formation of novel evolutionary lineages. There are two main variants of hybrid species genomes: allopolyploid, which have one full chromosome set from each parent species, and homoploid, which are a mosaic of the parent species genomes with no increase in chromosome number.
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