Question

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?

Answer 1

The answer would be 2!!

If having a bent thumb is a recessive trait controlled by a single gene, an individual must have two recessive alleles to express the trait. Alleles are different versions of a gene, and in this case, the "bent thumb" trait is recessive, meaning that it is only expressed when an individual has two copies of the recessive allele.

To understand this concept better, let's denote the dominant allele for a straight thumb as "S" and the recessive allele for a bent thumb as "s." If an individual has two dominant alleles (SS), they will not have a bent thumb. However, if an individual has one dominant allele and one recessive allele (Ss), they will not have a bent thumb but will be a carrier of the recessive allele. Only when an individual has two recessive alleles (ss) will they express the trait and have a bent thumb.

Therefore, a person must have two recessive alleles (ss) to have a bent thumb.

I hope you are having a great day, you can do this!! :) <3

Answer 2

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.