Genome analysis of ground squirrels of the genus Citellus (Rodentia, Sciuridae) I. DNA reassociation kinetics and genome size of eight species

Abstract

Kinetic of reassociation of short DNA fragments were measured in eight ground squirrel species: Citellus undulatus, C. parryL C. relictus, C. dauricus, C. citellus, C. pygmaeus, C. fulvus and C. major. It was shown that 30-50% of their genome were represented by repeated sequences forming three kinetic fractions, i,e., very fast(Cot< 10 3), fast(Cot 10 -3 -3 × I0 -l) and intermediate (Cot 6 × 10 -1 -6 × 101). Based on parameters of DNA reassociation kinetics genome sizes of Citellus were estimated to range from 2.7 pg (C. dauricus) to 3.9 pg (C. pygmaeus and C.fulvus). Variation in genome sizes involves both the repeated and the non-repeated sequence components to approximately equal extents in all the species except C. dauricus. The linear quantitative relation between C-banding heterochromatin and both very fast and fast reassociated DNA fractions was established, but no connection with the intermediate fraction was found. No distinct relation was revealed between parameters of DNA reassociation kinetics and taxonomic status of species within genus or with the chromosome number of the karyotype.

Genome analysis of ground squirrels of the genus Citellus (Rodentia, Sciuridae) II. DNA sequence organization

“…In addition, reassociation kinetics of long (10 kb) fragments only was studied in C. major. Figure I also for sake of comparison presents the reassociation curves of short fragments (0.25 -0.30 kb), a detailed analysis of which was presented in our previous paper (Ginatulina et al, 1982). The same components of DNA that were isolated using short fragments can be identified in the kinetic reassociation curves of long fragments, i.e.…”

“…Goldberg et al, 1975). The rationale of this method is that in analyses of reassociation kinetics by hydroxyapatite chromatography the rate of reassociation is dependent on degree of repetitiveness and DNA fragment length.…”

“…All data are given with correction to 100% level of DNA fragments rcassociation. Reassociation data of short fragments (0.25 0.30 kb) taken from the previous paper (Ginatulina et al, 1982). In the variation of the relative sizes of the four kinetic fractions with fragment length Citellus ma-/or resembles C. pygmaeus and C. fuh,us more than C. parrvi and C. undulatus.…”

“…The molecular structure of the genome was previously studied in some representatives of the genus and quantitative variation both of the total DNA content of the genome (2.7--3.9 pg per haploid set of chromosomes) and of its separate fractions was demonstrated (Ginatulina et aL, 1982). A direct quantitative relationship was also established between the C-banded heterochromatin and repeated sequences (Lyapunova et aL, 1980;Ginatulina et al, 1982).…”

“…This genus is distinguished by a well studied morphology, palaentology and karyology (cf. Ginatulina et al, 1982). The molecular structure of the genome was previously studied in some representatives of the genus and quantitative variation both of the total DNA content of the genome (2.7--3.9 pg per haploid set of chromosomes) and of its separate fractions was demonstrated (Ginatulina et aL, 1982).…”