Left thumb over right is dominant, and is represented with a capital C. Right thumb over left is recessive, and is represented with a lowercase c.

What would be the genotype of a person who naturally crosses his right thumb over his left when folding his hands together?

A) cc

B) Cc

C) CC or cc

D) CC or Cc

Answer: Option A) cc

Explanation:

For a given gene, there are 2 or more alternative forms present, and they are known as alleles. The alleles are of two types - dominant and recessive. The dominant allele is the one which expresses itself in both heterozygous and homozygous condition in the phenotype. The recessive allele is the one which is only able to express itself in homozygous condition. Since, the right thumb over left allele c is recessive, the person who crosses right thumb over left must be a homozygote, and hence his genotype should be cc.