Question

dihybrid crosses- crosses in which inheritance of two characters are studied
in humans, free ear lobes e are dominant to attached ear lobes e, and the allele for hypercholesterolemia h is dominant to the normal condition h.
hypercholesterolemia results in severely elevated blood cholesterol levels and high risk of heart attack. what gametes can be produced by the following
parents eehh x eehh and what are the expected phenotypic and genotypic ratios for the offspring produced. explain your answer using punnett square.

Explanation:

Step1: Determine gametes

For \(EeHH\):

• For the \(E/e\) gene: \(E\) and \(e\)
• For the \(H/h\) gene: \(H\) (since it is \(HH\))
• Gametes: \(EH\) and \(eH\)

For \(eeHh\):

• For the \(E/e\) gene: \(e\) (since it is \(ee\))
• For the \(H/h\) gene: \(H\) and \(h\)
• Gametes: \(eH\) and \(eh\)

Step2: Create Punnett square

	\(EH\)	\(eH\)
\(eh\)	\(EeHh\)	\(eeHh\)

Step3: Determine genotypes

• \(EeHH\): \(1/4\)
• \(eeHH\): \(1/4\)
• \(EeHh\): \(1/4\)
• \(eeHh\): \(1/4\)

Step4: Determine phenotypes

• Free earlobes, hypercholesterolemia (\(EeHH\) and \(EeHh\)): \(2/4 = 1/2\)
• Attached earlobes, hypercholesterolemia (\(eeHH\) and \(eeHh\)): \(2/4 = 1/2\)

Answer:

• Gametes: \(EeHH\) produces \(EH\) and \(eH\); \(eeHh\) produces \(eH\) and \(eh\)
• Genotypic ratio: \(EeHH : eeHH : EeHh : eeHh = 1:1:1:1\)
• Phenotypic ratio: Free earlobes, hypercholesterolemia : Attached earlobes, hypercholesterolemia = \(1:1\)