The origin of the genetical diversity of Microtus mandarinus chromosomes

Abstract

Here we describe our comparative studies on two types of X chromosomes, namely X(M) and X(SM,) of the mandarin vole (Microtus mandarinus). By chromosome G- and C-banding analysis, we have found that two different types of X chromosomes exist in mandarin voles. The two types of X chromosomes present two different G- and C-banding patterns: the X(M) chromosome is a longer metacentric X chromosome which is C-band negative; and the X(SM) is a shorter submetacentric X chromosome which has one C-band at the centromere and another one at the middle part of the short arm. The X(SM) has 6 G-bands including one on the kinetochore, one in the middle of the short arm, and four on the long arm. The X(M) has 7 G-bands including one on the kinetochore, two on the short arm, and four on the long arm. We have further found that female voles can be grouped into three types based on the composition of the X chromosome but the male voles have only one type. The three female groups are: (1) female voles (X(M)X(SM)), in which the two X chromosomes are different, the longer one is metacentric and the shorter is submetacentric; (2) female vole (X(SM)X(SM)), in which the two X chromosomes are both submetacentric; (3) female vole (X(M)O), in which there is only one X chromosome that is metacentric. Surprisingly, we have never found female voles with X(M)X(M), females with X(SM)O or males with X(M)Y. We hypothesize that the X(SM) chromosome is derived from the X(M) through its breakage and re-joining. The paper also discusses the formation of X(M)O females.

Two new karyotypes and bandings in Microtus mandarinus faeceus (Rodentia)

“…1, 2). Heteromorphic X chromosomes also exist in karyotypes of M. mandarinus captured from Russia and Lingbao and Wendeng in China (KOVALSKAYA et al 1974;ZHU et al 2003;WANG et al 2003).A new karyotype 2n ϭ 50 ϭ 4sm ϩ 43t ϩ 1m ϩ xx (sm,sm) with the sex chromosomse X SM X SM Our analysis of the chromosomes of M. m. faeceus revealed a new karyotype. The second pair of autosomes (no.…”

“…We analyzed the metaphases and C-banded karyotypes of female X ST O and male X M Y of M. m. faeceus , and found that the typical C-banding pattern of autosomes was as only one type of sex chromosome combination, X SM Y (ZHU et al 2003). In a previous study we found 22 females with XO type among 70 individuals analyzed.…”

“…1, 2). Heteromorphic X chromosomes also exist in karyotypes of M. mandarinus captured from Russia and Lingbao and Wendeng in China (KOVALSKAYA et al 1974;ZHU et al 2003;WANG et al 2003).…”

“…We know that the chromosome number of M. m. faeceus of Lingbao is from 49 to 52, and the value of NF is from 54 to 55 (ZHU et al 2003). The chromosome number of M. m. faeceus of Jiangyan is from 47 to 50, and the value of NF is from 53 to 55.…”

Numerical and structural variations of the X chromosomes and no. 2 autosomes in mandarin vole, Microtus mandarinus (Rodentia)

“…Heteromorphic X chromosomes also exist in karyotypes of M . mandarinus captured from Russia, Lingbao and Wendeng in China (Table 2) (K ovalskaya et al 1974; Z hu et al 2003a; W ang et al 2003). G‐banding staining showed that the X ST had eight G‐bands including one on the short arm, and seven on the long arm (Fig.…”