Encyclopedia of Genetics, Genomics, Proteomics and Informatics

2008 Edition

Chromosome Numbers

Reference work entry
First Online:
DOI: https://doi.org/10.1007/978-1-4020-6754-9_3004
Download entry PDF
How to cite
Chromosome numbers are variable among the different species and although the numbers may vary, they are important and stable taxonomic features (see Table C5). The basic number is represented by x, the gametic number by n, and the somatic number by 2n. Thus in a diploid species like Arabidopsis x = 5 = n. In hexaploid wheat 6x = 2n. The chromosome number may vary between males and females as a mechanism of sex determination. Also, centromeric fusion may generate one bi-armed chromosome from two telocentrics (acrocentric) or the opposite may take place. In cultured cells of mice the chromosomes may become acrocentric and double in number. The majority of bacteria have a single circular chromosome. Some other species, e.g., Rhodobacter sphaeroides, Agrobacterium tumefaciens, Brucella melitensis, Vibrio cholerae also have multiple chromosomes. Chromosome numbers of organisms often studied in genetics are shown here and additional numbers are found under the English (or scientific) name of different organisms.  genome,  polyploid,  haploid,  acrocentric,  telocentric,  chromosome arm,  sex chromosomes,  Robertsonian translocation
Table C5.

Chromosome numbers

MICROORGANISMS

x

 

Aspergillus nidulans

8

 

Chlamydomonas reinhardi

8

 

Dictyostelium discoides

7

 

Neurospora crassa

7

 

Saccharmoyces cerevisiae

16

 

Saccharomyces pombe

3

 

PLANTS

  

Arabidopsis thaliana

5

 

Barley (Hordeum vulgare)

7

 

Broad bean (Vicia faba)

6

 

Datura sp.

12

 

Epilobium sp.

18

 

Haplopappus gracilis

2

 

Lily (Lilium sp.)

12

 

Maize (Zea mays)

10

 

Oenothera lamarckiana

7

 

Petunia hybrida

7

 

Potato (Solanum tuberosum, 2n = 48 = 4x)

12 + 12

 

Tobacco (Nicotiana tabacum, 2n = 48 = 4x)

12 + 12

 
 

12

 

(Nicotiana plumbaginifolia, 2n = 24)

  

Tomato (Lycopersicum sp.)

12

 

Wheat (Triticum aestivum, 2n = 42 = 6x)

7 + 7 + 7

 
 

7 + 7

 

(Triticum turgidum, 2n = 24 = 4x)

  
 

7

 

(Triticum monococcum, 2n = 14)

  

ANIMALS

  

Cattle (Bos taurus)

30

 

Caenorhabditis elegans (female 2n = 12, male 2n = 11)

6

 

Chimpanzee (Pan troglodytes)

24

 

Cricket (Gryllus campestris, female 2n = 30, male 2n = 29)

15

 

Drosophila melanogaster

4

 

Hamster (Mesocricetus auratus)

22

 

Honeybee (Apis mellifera, female 2n = 32, male 1n = 16)

16

 

Housefly (Musca domestica)

6

 

Homo sapiens

23

 

Mouse (Mus musculus)

20

 

Rat (Rattus norvegicus)

21

 

Sea urchin (Strongylocetrotus purpuratus)

18

 

Silkworm (Bombyx mori)

28

 

Swine (Sus scrofa)

19

 

Tetrahymena pyriformis

5

 

Toad (Xenopus laevis)

18

 

Wasp (Habrobracon sp., female 2n = 20, male 1n = 10)

10

 

Copyright information

© Springer Science+Business Media 2008