Question

1. in dogs, there is a hereditary type of deafness caused by a recessive gene. two dogs who carry the gene for deafness but have normal hearing are mated. complete the punnett square and list the percent chances of each genotype.

percent chance

Explanation:

Step1: Define genotype notation

Let the dominant (normal hearing) allele = $D$, recessive (deafness) allele = $d$. Both parent dogs are carriers, so their genotype is $Dd$.

Step2: Set up Punnett Square

	$D$	$d$
$d$	$Dd$	$dd$

Step3: Count genotype frequencies

Total Punnett Square cells = 4.

• $DD$ count = 1, frequency = $\frac{1}{4}$
• $Dd$ count = 2, frequency = $\frac{2}{4}=\frac{1}{2}$
• $dd$ count = 1, frequency = $\frac{1}{4}$

Step4: Convert to percentages

Percent = frequency $\times 100\%$

• $DD$: $\frac{1}{4} \times 100\% = 25\%$
• $Dd$: $\frac{1}{2} \times 100\% = 50\%$
• $dd$: $\frac{1}{4} \times 100\% = 25\%$

Answer:

Completed Punnett Square and percent chances:

	$D$	$d$	Percent Chance
$d$	$Dd$	$dd$	$Dd$: 50% <br> $dd$: 25%

Final genotype percent chances:

• Homozygous dominant ($DD$): 25%
• Heterozygous carrier ($Dd$): 50%
• Homozygous recessive ($dd$): 25%