Question

genetics

If Drosophila, the oval (ov) locus is on the X-chromosome. Recessive mutants make the eyes oval instead of the normal round. Furthermore, it is known that when two mutations occur within the oval gene, the phenotype is a more extreme oval phenotype. The genes sn and v are closely linked to the right and left of oval, respectively. Two single mutations ov1 and ov3 were obtained and used in the following experiments. In 10,000 progeny of a female of the genotype sn ov1 v/+ ov3 + and a wild type male, most males had the regular oval eyes, but two males had wild type eyes and were sn phenotype and three males had extreme oval eyes and were of the v phenotype (sn and v are recessive and + indicates the normal alleles).

Answer 1

From a pair attached X chromosomes of Drosophilia melanogaster there is derived occasionally a single detached X chromosome which shows all the characters ofanormal X. In consequence a very small class of regular offspring is found attached in X chromosomes mated to scute broad apricot males produced a regular wild type female.

The attachment ofthe ends of the X chromsome affords a new situation for crossing over and are mot represented by usual classes.