Friday, March 14, 2008

Number of chromosomes in various organisms


These tables give the total number of chromosomes (including sex chromosomes) in a cell nucleus. For example, human cells are diploid and have 22 different types of autosomes, each present as two copies, and two sex chromosomes. This gives 46 chromosomes in total. Other organisms have more than two copies of their chromosomes, such as Bread wheat which is hexaploid and has six copies of 6 different chromosomes - 42 chromosomes in total.

Chromosome numbers in some plants
Plant Species #
Arabidopsis thaliana 10
Rye 14
Maize 20
Einkorn wheat (diploid)[22] 14
Durum wheat (tetraploid)[22] 28
Bread wheat (hexaploid)[22] 42
Wild tobacco[citation needed] 24
Cultivated tobacco 48
Adder's Tongue Fern (diploid)[23] approx 1,440
Chromosome numbers (2n) in some animals
Species # Species #
Common fruit fly 8 Guinea Pig[24] 64
Dove[citation needed] 16 Garden snail[25] 54
Earthworm Octodrilus complanatus[26] 36 Tibetan fox 36
Domestic cat 38 Domestic pig 38
Lab mouse 40 Lab rat 42
Rabbit[citation needed] 44 Syrian hamster 44
Hare[citation needed] 46 Human[27] 46
Gorillas, Chimpanzees[27] 48 Domestic sheep 54
Elephants[28] 56 Cow 60
Donkey 62 Horse 64
Dog[29] 78 Kingfisher[30] 132
Goldfish[31] 100-104 Silkworm[32] 56
Chromosome numbers in other organisms
Species Large
Trypanosoma brucei 11 6 ~100
Chicken[33] 8 2 sex chromosomes 60

Normal members of a particular eukaryotic species all have the same number of nuclear chromosomes (see the table). 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.

The 24 human chromosome territories during prometaphase in fibroblast cells.
The 24 human chromosome territories during prometaphase in fibroblast cells.

Asexually reproducing species have one set of chromosomes, which is the same in all body cells.

Sexually reproducing species have somatic cells (body cells), which are diploid [2n] having two sets of chromosomes, one from the mother and one from the father. Gametes, reproductive cells, are haploid [n]: they have one set of chromosomes. Gametes are produced by meiosis of a diploid germ line cell. During meiosis, 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 (fertilization), a new diploid organism is formed.

Some animal and plant species are polyploid [Xn]: they have more than two sets of homologous chromosomes. Agriculturally important plants such as tobacco or wheat are often polyploid compared to their ancestral species. Wheat has a haploid number of seven chromosomes, still seen in some cultivars as well as the wild progenitors. The more common pasta and bread wheats are polyploid, having 28 (tetraploid) and 42 (hexaploid) chromosomes compared to the 14 (diploid) chromosomes in the wild wheat.[34]


Prokaryote species generally have one copy of each major chromosome, but most cells can easily survive with multiple copies.[35] Plasmids and plasmid-like small chromosomes are, like in eukaryotes, very variable in copy number. The number of plasmids in the cell is almost entirely determined by the rate of division of the plasmid - fast division causes high copy number, and vice versa.

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