Question

1. in guinea pigs, the allele for short hair is dominant. what genotype would a pure breeding short haired guinea pig have? what genotype would a heterozygous short haired guinea pig have? what genotype would a long - haired guinea pig have? show a cross between two heterozygous guinea pigs. what percentage of the offspring will have short hair? what percentage of the offspring will have long hair?

Explanation:

Step1: Determine genotypes

Let \( S \) represent the dominant allele (short - hair) and \( s \) represent the recessive allele (long - hair).
A pure - breeding short - haired guinea pig has two dominant alleles. So its genotype is \( SS \).
A heterozygous short - haired guinea pig has one dominant and one recessive allele. So its genotype is \( Ss \).
A long - haired guinea pig has two recessive alleles. So its genotype is \( ss \).

Step2: Perform the cross

When crossing two heterozygous \( Ss\times Ss \), the Punnett square is:

Gametes of Parent 1	Gametes of Parent 2
\( S \)	\( SS \) (short - hair)	\( Ss \) (short - hair)
\( s \)	\( Ss \) (short - hair)	\( ss \) (long - hair)

Step3: Calculate percentages

The genotypes of the offspring are \( SS:Ss:ss = 1:2:1 \).
The number of short - haired offspring (\( SS + Ss \)) is \( 3 \) out of \( 4 \). So the percentage of short - haired offspring is \( \frac{3}{4}\times100\%=75\% \).
The number of long - haired offspring (\( ss \)) is \( 1 \) out of \( 4 \). So the percentage of long - haired offspring is \( \frac{1}{4}\times100\% = 25\% \).

Answer:

• Genotype of pure - breeding short - haired guinea pig: \( SS \)
• Genotype of heterozygous short - haired guinea pig: \( Ss \)
• Genotype of long - haired guinea pig: \( ss \)
• Percentage of short - haired offspring: \( 75\% \)
• Percentage of long - haired offspring: \( 25\% \)