Question

what are the chances of a daughter inheriting a recessive x - linked disease if her mother is a symptomless carrier and her father has the disease?
(a) 100%
(b) 50%
(c) 25%
(d) 0
question 8
a man with hemophilia can pass hemophilia on to his sons.
(a) true
(b) false
question 9
if the heterozygous phenotype is intermediate between those of the two different homozygotes, this is called:
(a) codominance
(b) incomplete dominance
(c) independent assortment
(d) epistasis

Explanation:

Question 7

Step1: Understand X - linked inheritance

Let \(X^h\) represent the allele for the recessive X - linked disease and \(X^H\) represent the normal allele. The mother is a carrier (\(X^H X^h\)) and the father has the disease (\(X^hY\)). Daughters inherit one X - chromosome from each parent.

Step2: Determine possible genotypes of daughters

The possible genotypes of daughters are \(X^H X^h\) (from mother's \(X^H\) and father's \(X^h\)) and \(X^h X^h\) (from mother's \(X^h\) and father's \(X^h\)). The probability of getting \(X^h\) from the mother is \(\frac{1}{2}\) and from the father is 1. The probability of a daughter having the disease (\(X^h X^h\)) is \(\frac{1}{2}\) or 50%.

Question 8

Step1: Recall X - linked inheritance in males

Hemophilia is an X - linked recessive disorder. Males have the genotype \(XY\). They pass their Y - chromosome to their sons and their X - chromosome to their daughters. So, a man with hemophilia (\(X^hY\)) cannot pass hemophilia (\(X^h\)) to his sons as sons receive the Y - chromosome from their father.

Question 9

Step1: Recall genetic concepts

Codominance is when both alleles in a heterozygote are fully expressed. Independent assortment is the random distribution of non - homologous chromosomes during meiosis. Epistasis is when one gene masks or modifies the expression of another gene. Incomplete dominance is when the heterozygous phenotype is intermediate between the two homozygous phenotypes.

Answer:

Question 7: B. 50%
Question 8: B. False
Question 9: B. Incomplete dominance