Having a bent thumb is a recessive trait in humans. The trait is controlled by a single gene. How many recessive alleles must a person have to have a bent thumb?

The answer is; 2

This is because humans are diploid organisms - meaning they have two sets of chromosomes each carrying one of the sets of gene alleles. The expression of a recessive allele is masked by the sister dominant allele, i. e if an individual has both of the alleles. However, for the recessive allele to be expressed, the individual must have both alleles being recessive.

2

Explanation:

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