1 The concordance among identical twins for autosomal domina

1. The concordance among identical twins for autosomal dominant disorder caused by a single gene, (assuming mutations came from ancestors many generations ago) would be close to:

a. 100%

b. 50%

c. 75%

d. 10%

e. 25%

2. The concordance among fraternal twins for autosomal dominant disorder caused by a single gene, (assuming mutations came from ancestors many generations ago) would be close to:

a.100%

b. 50%

c. 80%

d. 10%

e. 25%

3. The concordance among identical twins for autosomal recessive disorder caused by a single gene, (assuming mutations came from ancestors many generations ago) would be close to:

a. 100%

b.50%

c.75%

d.10%

e.25%

4. The concordance among fraternal twins for autosomal recessive disorder caused by a single gene, (assuming mutations came from ancestors many generations ago) would be close to:

a.100%

b.50%

c.75%

d.10%

e.25%

Solution

1. 100%.

for diseases caused by a single gene, concordance among identical twins should be 100%.

2. 50%

For fraternal twins, concordance for dominant disorders is expected to be 50%, assuming only one parent is heterozygous for the disease.

3.

4. 25%.

For recessive diseases, concordance among fraternal twins would be 25% if both are heterozygous.