Linked genes and recombination Transitional Reasoning Download PDF

Questions

1. 1.

   A researcher testcrosses a dihybrid female fruit fly heterozygous for gray body ($B/b$) and normal wings ($V/v$) with a homozygous recessive male displaying a black body and vestigial wings ($bbvv$). The resulting 1,000 offspring comprise 415 gray body with normal wings, 405 black body with vestigial wings, 92 gray body with vestigial wings, and 88 black body with normal wings. Based on these data, what can be definitively concluded about the chromosomal arrangement and genetic distance of these two gene loci?

   • A) The genes are linked on the same chromosome in cis conformation with a map distance of 18 map units (cM) between them.
   • B) The genes assort independently on non-homologous chromosomes, and deviations from the expected 1:1:1:1 ratio result from selective developmental lethality.
   • C) The genes are linked on the same chromosome in trans conformation with a recombination frequency establishing a genetic distance of 82 cM.
   • D) The genes exhibit complete linkage with no crossing over occurring during gametogenesis, leaving the non-parental phenotypes to arise from spontaneous mutation.