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26:08Genes A, B, and C are linked on a chromosome and found in the order A–B–C. Genes A and B recombine with a frequency of 8%, and genes B and C recombine at a frequency of 24%. For the cross a⁺b⁺c/abc⁺ × abc/abc, predict the frequency of progeny genotypes. Assume interference is zero.
Gene G recombines with gene T at a frequency of 7%, and gene G recombines with gene R at a frequency of 4%.
Draw two possible genetic maps for these three genes, and identify the recombination frequencies predicted for each map.
Gene G recombines with gene T at a frequency of 7%, and gene G recombines with gene R at a frequency of 4%.
Assuming that organisms with any desired genotype are available, propose a genetic cross whose result could be used to determine which of the proposed genetic maps is correct.
Genes A, B, C, D, and E are linked on a chromosome and occur in the order given.
Previous genetic linkage crosses have determined that recombination frequencies are 6% for genes A and B, 4% for genes B and C, 10% for genes C and D, and 11% for genes D and E. The sum of these frequencies between genes A and E is 31%. Why does the recombination distance between these genes as determined by adding the intervals between adjacent linked genes differ from the distance determined by the test cross?
Syntenic genes can assort independently. Explain this observation.
Define linkage disequilibrium. What is the physical basis of linkage, and what causes linkage equilibrium? Explain how crossing over eliminates linkage disequilibrium.
