Question

In humans, red hair is a recessive trait. The following pedigree displays the inheritance of red hair within a family. Utilize the pedigree to determine the genotype for individual I-2.

A) RR
B) Rr
C) rr
D) Cannot be determined

Answer 1

In humans, red hair is a recessive trait. The genotype for individual I-2 in the pedigree is Rr.

Step-by-step explanation:

In humans, red hair is a recessive trait, meaning that it is only expressed when an individual has two copies of the recessive allele.

Looking at the pedigree, we can see that individual I-1 has red hair. Since red hair is recessive, I-1 must have two copies of the recessive allele (rr).

Individual I-2, who is the offspring of two individuals with red hair (I-1 and I-3), will inherit one allele from each parent. Since I-1 is rr, I-2 must have inherited one copy of the recessive allele (r) from I-1 and one copy of the recessive allele (r) from I-3. Therefore, the genotype for individual I-2 is Rr.

The fact that two individuals with red hair would have the genotype 'rr' since red hair is a recessive trait that is not expressed unless both alleles are recessive. If individual I-2 did not have genotype 'rr,' they would not express the red hair phenotype. Thus, without needing the specific pedigree chart for analysis, we understand that for a trait that is recessively inherited, expressing individuals are always homozygous recessive (rr).

Therefore, the correct answer is B) Rr.