Question

Which of the following is true regarding the expression of a chromosomal genetic mutation that is expressed on a recessive allele?
A. The mutation will be expressed only in individuals that are heterozygous for the gene.
B. The mutation will be expressed approximately 50 percent of the time.
C. The mutation will be expressed consistently when the mutation occurs on a recessive allele.
D. The mutation will be expressed only if the individual has two copies of the recessive allele.

Answer 1

D. The mutation will be expressed only if the individual has two copies of the recessive allele.

Answer 2

Answer:

Option D, The mutation will be expressed only if the individual has two copies of the recessive allele

Explanation:

A characteristic or trait associated with a dominant allele is expressed when the genotype is heterozygous or homozygous dominant .

But a characteristic or trait associated with a recessive allele is expressed only when the genotype is  homozygous recessive. Homozygous recessive means that an individual must have a genotype that has two copies of the recessive allele.

For example

If R represents dominant red color of flower and r represents the recessive white color of flower, then genotye "RR" and "Rr" represents homozygous & heterozygous dominant genotype respectively.

While "rr" represents the homozygous recessive genotype.

Thus, option D is correct