In a genetic cross of two heterozygous pea plants (Tt × Tt) where the gene T for tallness is located on a chromosome that undergoes 2 crossover events between the T locus and a nearby gene D for disease resistance, what is the probability that a gamete carries the dominant allele T and the recessive allele d?
Answer
0.25
The correct answer is 0.25 — Hence the probability of obtaining a gamete with T and d is 1/4 or 0.25.
Step-by-step solution
- Because two crossovers occur between T and D, the alleles are returned to their parental arrangement (even number of crossovers restores the original combination).
- The parental gamete types are T D, T d, t D, and t d, each occurring with equal probability 1/4.
- Hence the probability of obtaining a gamete with T and d is 1/4 or 0.25.
Common mistake: Believing that an even number of crossovers causes recombination between the loci
Concept tested: Recombination and crossover effects
Published · How this solution was prepared and checked
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