Question

Suppose that seed size in a particular plant species is a polygenic trait. A grower crosses two different pure-breeding varieties of the plant, and measures seed size in the F1 progeny. She then backcrosses the F1 plants to one of the parental varieties and measures seed size in the backcross progeny. The grower finds that seed size in the backcross progeny has a higher variance than seed size in the F1 progeny. What is the most likely explanation for the higher seed size variability in the backcross progeny?

The backcross progeny are uniformly heterozygous at all seed size loci.
The backcross progeny have more mutations because they result from more cell divisions.
Unlike the F1 generation, the backcross progeny are homozygous recessive.
Unlike the F1 generation, the backcross progeny are homozygous dominant.
The backcross progeny are not uniformly heterozygous at the seed size loci.

Answer 1

The most likely explanation for the higher seed size variability in the back cross progeny is the backcross progeny are not uniformly heterozygous at the seed size loci.

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