Question

1. in guinea pigs, the allele for rough coat (r) is dominant over the allele for smooth coat (r). a homozygous dominant guinea pig and a homozygous recessive guinea pig are mated. which of the following shows the possible genotypes of their offspring?

options:
rr and rr
rr, rr, and rr
rr
rr

Explanation:

Step1: Determine Parental Genotypes

The homozygous dominant guinea pig has genotype \( RR \) (since dominant allele is \( R \) and homozygous means two identical dominant alleles). The homozygous recessive guinea pig has genotype \( rr \) (two identical recessive alleles \( r \)).

Step2: Analyze Gamete Production

The \( RR \) parent can only produce gametes with the \( R \) allele (because all its alleles are \( R \)). The \( rr \) parent can only produce gametes with the \( r \) allele (because all its alleles are \( r \)).

Step3: Determine Offspring Genotypes

When these gametes combine, each offspring will receive one \( R \) from the dominant parent and one \( r \) from the recessive parent. So the genotype of all offspring will be \( Rr \) (since \( R \) from one parent and \( r \) from the other combine).

Answer:

The possible genotype of their offspring is \( Rr \), so the correct option is the one with \( Rr \) (the option labeled with \( Rr \) among the choices).