Question

3.Another patient has a family history in which:

1. the disease was equally distributed among the male

and female offspring of affected females

2. all daughters of an affected male were affected

3. none of the sons of an affected male and unaffected

female were affected

What type of inheritance is this likely to be?

A. Autosomal dominant

B. Autosomal recessive

C. X-linked dominant

D. X-linked recessive

4. Another patient has a family history in which:

1. carrier females transmit the trait to half of their

sons

2. none of the carrier females daughters were

affected, but half were carriers

What type of inheritance is this likely to be?

A. Autosomal dominant

B. Autosomal recessive

C. X-linked dominant

D. X-linked recessive

5. Another patient has a family history in which:

1. males and females were equally affected

2. two of the offspring from two unaffected parents

were affected, while the other six offspring were

unaffected.

What type of inheritance is this likely to be?

A. Autosomal dominant

B. Autosomal recessive

C. X-linked dominant

D. X-linked recessive

Answer 1

3) this disease is X-linked dominant

.a) the disease was equally distributed among the male and female offspring of affected females:

both males and females inherit an X chromosome from mother, here hen mother is affected half of the sons are affected and half of the female offsprings are affected, means the female had mutation in one of the X chromosome and those offsprings which inherited mutant X chromosome ( there is equal chance to get one of these chromosomes so half of the progeny are affected and half are normal)

b) all daughters of an affected male were affected

daughters inherit one of their X chromosomes from their father if the father has dominant mutation in his X chromosome all of his daughters are affected

c) none of the sons of an affected male and unaffected

sons inherit the Y chromosome from father so sons of father having mutation in the X chromosome cannot be affected

so this is c) X-linked dominant

4) this X-linked recessive

.a) carrier females transmit the trait to half of their sons

females have 2 X-chromosomes so if they have a recessive mutation in one of their X chromosome females are not affected but they pass the affected chromosome to their sons

b) none of the carrier females daughters were affected, but half were carriers

females inherit one of their X chromosomes from father if the father is normal then all of his daughters will have normal X chromosome but half of them can inherit the affected chromosome from their mother, so half of them are carriers

so the answer is D) X-linked recessive