Chromosomal banding pattern and idiogram of the cotton rat,Sigmodon arizonae (Rodentia,Muridae)

A procedure for obtaining G-bands on chromosomes of mammals is outlined. The procedure was utilized in an investigation of the idiogram and banding pattern of the mitotic chromosomes of the cotton rat, Sigmodon arizonae. The diploid number of this species is 22, and each pair of homologues is easily separated on the basis of size, centromeric position, and banding pattern. The autosomes are represented by four pairs of large submetacentric chromosomes, three pairs of medium to small submetacentric chromosomes, two pairs of large subtelocentric chromosomes and one pair of small acrocentric chromosomes. The X chromosome is acrocentric and averages from 5.42% to 5.46% of the haploid female complement. The Y chromosome is a minute acrocentric and easily separated from the smallest acrocentric autosome. The usefulnes of Sigmodon arizonae as a laboratory animal for cytogenetic studies is substantiated.