The effects of Robertsonian fusions on chiasma frequency and distribution in the house mouse (Mus musculus domesticus) from a hybrid zone in northern Scotland

CLAUDIO J. BIDAU; MABEL D. GIMENEZ; CHRISTIANNE L. PALMER; JEREMY B. SEARLE

HEREDITY

NATURE PUBLISHING GROUP

Lugar: Londres; Año: 2001 vol. 87 p. 305 - 313

0018-067X

Chiasma frequency and distribution were studied in male Mus musculus domesticus from the John O´Groats -standard chromosomal hybrid zone in northern Scotland. Individuals of the John O´Groats race (2n = 32, homozygous for the Robertsonian fusions 4.10, 6.13, 9.12 and 11.14) and the standard race (2n = 40, all telocentric), and hybrids with various karyotypes, were examined. Chiasma frequency was signifcantly negatively correlated with the number of Robertsonian configurations in the meiotic cell. The decrease of chiasma frequency can be attributed to intrachromosomal effects that reduce the number of chiasmata in Robertsonian bivalents (formed in homozygotes for Robertsonian fusions) and trivalents (formed in heterozygotes). However, the reduction is more pronounced Robertsonian bivalents and is related to a shift of chiasmata to the distal ends of the chromosome arms. A different type of repatterning occurs in trivalents where there is a signifcant increase in proximal and interstitial chiasmata.