Spring Genetics 2026 Worksheet 3 Key
1. We say that crossing over is reciprocal. What does that mean for the products of
crossing over.
Equal parts of the chromatid are exchanged
2. Explain how, if the chromatids of two homologous chromosomes crossover 100%
of the time, it gives a recombination frequency of 50%.
Answer You have two parental chromatids and 2 recombinant chromatids after the
cross.
3. If, given the genotype of the individual as A—B/a—b, we get 50% crossover,
what should kinds of gametes should be produced and in what ratios?
¼ AB ¼ ab ¼ Ab ¼ aB
4. Recombination frequencies = map distances meaning how far two genes on the
same chromosome are apart. Explain Recombination frequency is related to how far
two genes are apart.
Answer the frequency of recombination increases with increasing distance between
genes.
