Comparative study of spontaneous and FUdR induced chromosomal instability in Pakistani Lohi and British Suffolk sheep - An indication of environmental mutagenesis

A study to compare the extent of geno-environmental interaction expressed as fragile sites was carried out in british suffolk and pakistani lohi breeds of sheep (ovis aries). spontaneous and 5-fluorodeoxyuridine (fudr) induced fragile sites were scored in metaphase chromosomes in two flocks of sheep reared under different environmental conditions. means and standard errors for aberrant cell count (ac) and number of aberrations (noa) per animal revealed highly significant differences between the two groups (p<0.01) belonging to distant continents of the globe. average number of cells with gaps and breaks (ac) was 0.56±0.15 vs 1.91± 0.34 whereas noa index per cell averaged 0.59±0.16 vs 2.36±0.48 in chromosomes grown in control cultures of lohi and suffolk breeds respectively. corresponding means in fudr synchronized chromosomes were 2.18±0.33 vs 13.26±0.85 and 2.65±0.50 vs 21.87±1.88 in the two breeds respectively. distribution comparison of chromosomal fragile sites grown in control cultures with no fudr revealed seven fragile bands in lohi compared to 24 in suffolk. microscopic analysis for the number of fragile bands in fudr treated chromosomes revealed 29 and 78 autosomal bands in lohi and suffolk breeds respectively. similarly the number of significantly fragile bands was 4 and 78 in the two breeds respectively. x-chromosome in lohi was highly stable in control as well as fudr cultures expressing no gaps and breaks whereas the suffolk x expressed 4 fragile bands. the study suggested that long term exposure of the two flocks to entirely variable environment might have played a significant role for higher chromosomal damage in the suffolk breed. copyright 2012 zoological society of pakistan.