1. The flower color (purple vs. red) and pollen shape (long vs. round) genes are linked so they do not assort independently
2. If the PO parents are genotype PPLL (purple/long) and ppll (red/round), then all their F1 offspring would be genotype PpLI (purple/long)
3. When two of these F1 offspring were bred to each other, their offspring (the F2 generation) would not show the 9:3:3:1 phenotype ratio expected from
unlinked genes that assort independently:
• Purple/long: expected ~203/361 (9/16th), observed 284/361
• Purple/round: expected ~68/361 (3/16th), observed 21/361
• Red/long: expected ~68/361 (3/16th), observed 21/361
• Red/round: empected ~23 (1/16th), observed 55/361
I want you to consider what would happen if the experiment were done a little differently:
1. Assume the PO parents have the following genotypes/phenotypes:
• PO parent #1 = PPII (purple/round)
• PO parent #2 = ppLL (red/long)
2. All F1s would still have the genotype PpLl; now, predict what would happen if you bred two of the F1s together to generate an F2 generation and answer
the following questions:
• If the genes were not linked, how many of each of the following phenotypes would you expect to see in the F2? (Assume 361 total offspring)
I. Purple/long:
II. Purple/round:
III. Red/long:
IV. Red/round:
• Since the genes for flower color and pollen shape are linked, which phenotype(s) would you expect to be more abundant than expected? Explain why.
• Since the genes for flower color and pollen shape are linked, which phenotype(s) would you expect to be less abundant than expected? Explain why.
• Which genotypes in the F2 generation could only be seen if crossing over happened during gamete generation in the F1 plants? (Recall that the gametes
in the F1 are what deliver the alleles to the F2 plants.)
