Mendelian ratios are modified in crosses involving autotetraploids. In wheat, th
ID: 163192 • Letter: M
Question
Mendelian ratios are modified in crosses involving autotetraploids. In wheat, the brown seed trait is dominant to white seeds. A true-breeding brown seed plant (genotype WWWW) is crossed to a true-breeding white seed plant (genotype wwww). If F1 progeny (genotype WWww) are crossed to true-breeding white seed plants (wwww), what proportion of the F2 progeny do you expect to have white seeds? Assume that a single dominant W allele is sufficient to produce brown seeds, and that synapsis between any two chromosomes carrying a W or w allele is equally likely.
Explanation / Answer
Answer:gametes produced by the WWww heterozygote would be 1/6 WW,
1/6 ww,
and 4/6 Ww.
. All the ww gametes produced by the heterozygote, when they fuse with ww gametes produced by the wwww parent, will give rise to wwww (white seed) fF2 progeny, but none of the Ww or WW gametes.the answer is 1/6.