Daniel McDonald and Nancy Peer determined that eyespot (a clear spot in the center of the eye) in four beetles is caused by an X-linked gene (es) that is recessive to the allele for the absence of eyespot (95*).
They conducted a series of crosses to determine the distance between the gene for eyespot and a dominant X-linked gene for striped (St), which causes white stripes on females and acts as a recessive lethal (is lethal when homozygous in females or hemizygous in males). The cross below was carried out (D. J. McDonald and N. J. Peer, 1961. Journal of Heredity 52261—264).
Calculate the recombination frequency between es and St using the available data.
Are some potential genotypes missing among the ptogeny of the cross? If so, which ones and why?
• Both Stl Ymales and St] St females are missing due to lethality.
• One half of the female as St‘l es St‘recombinants are missing due to lethality.
• No potential genotypes are missing among the progeny.
• Both es + St l Y and as St l Y males are missing due to lethality.
• es + l es + females are missing bemuse they are linked to lethal St alleles.
