Genome size in two species of Calomys (Rodentia, Cristidae)

M.A. CICCIOLI Y L. POGGIO

GENETICS SELECTION EVOLUTION

BIOMED CENTRAL LTD

Año: 1993 vol. 25 p. 109 - 120

0999-193X

Summary - The DNA content of 2 related species, Calomys laucha Thomas (C 1) (2rc = 64, fundamental number = 74) and Calomys musculinus Fisher (C m) (2n = 38, fundamental number = 62) was studied using Feulgen microdensitometry using Mus domesticus as a control. Amounts of (haploid) DNA in the 2 species were significantly different (Cl: 6.940 pg; Cm: 6.202 pg; P < 0.05). The results were analyzed in relation to: the total diploid karyotype length measured from synaptonemal complexes with a light microscope (CI: 735.55 /µm; Cm: 446.30 /µm; P < 0.0001) and from mitotic metaphase chromosomes (CI: 222.074 /µm; Cm: 102.651 /µm; P < 0.0001), the metacentric-submetacentric autosome number (Cl: 8; Cm: 22) and the area of chromocenters showing positive staining with C-banding technique (heterochromatin) (Cl: 100%; Cm: 99.66%). The DNA amount in pg per unit length of karyotype (measured from synaptonemal complexes) is higher in Calomys musculinus (0.028 pg/µm) than in Calomys laucha (0.019 pg/µm). This indicates that there is not a constant amount of DNA associated with a given length of karyotype, which suggests that the difference between the 2 species may involve differential packing of DNA. This could be due to: genic differences; differential interactions between genes and the cellular environment; and/or alteration of gene expression following the formation of new linkage groups due to chromosomal rearrangements. Calomys musculinus C Calomys laucha C C-value / karyotype length / synaptonemal complex