Apentix/AP Biology/Unit 5: Heredity/Question

AP Biologyeasymcq1 pt

Genes A and B are located close to each other on the same chromosome. A heterozygous individual with the genotype A b / a B is crossed with a homozygous recessive individual. The observed offspring occur in a phenotypic ratio of approximately 40:10:10:40. What is the most likely explanation for this deviation from the expected 1:1:1:1 ratio?

Explanation

Core Concept

Because the genes are linked on the same chromosome, they do not assort independently. The high proportion of parental phenotypes (40:40) and the small proportion of recombinant phenotypes (10:10) indicate that crossing over occurred between the loci only occasionally.

Correct Answer

q8_C

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