ABMGG ABMGG Inheritance Patterns and Population Genetics

Question 1

In autosomal dominant inheritance, what is the recurrence risk for each offspring of an affected parent?

Accepted Answer

50%

Answer

An affected parent carries one pathogenic allele on one of the two autosomes; each child has a 50% chance of inheriting that allele.

Question 2

Which inheritance pattern is characterized by transmission exclusively through the maternal line with variable expressivity among family members?

Accepted Answer

Mitochondrial inheritance

Answer

Mitochondrial DNA is maternally inherited; all children of an affected mother may be affected but paternal transmission never occurs.

Question 3

A couple is each a carrier of the same autosomal recessive variant. What is the probability that their child will be an unaffected carrier?

Accepted Answer

50%

Answer

In a carrier × carrier cross, the expected genotypic ratio is 1 homozygous normal : 2 carriers : 1 affected, so carriers make up 2/4 = 50% of offspring.

Question 4

Genomic imprinting results in disease when:

Accepted Answer

Both copies of a gene are inherited from the same parent (uniparental disomy) or one copy's imprint is erased

Answer

Imprinted genes are expressed from only one parental allele; uniparental disomy or imprinting center defects silence both working copies, causing disease.

Question 5

What term describes the phenomenon where carrier females of an X-linked recessive condition are clinically affected due to skewed X-inactivation?

Accepted Answer

Manifesting carrier

Answer

When the normal X chromosome is preferentially inactivated in most cells, the carrier female expresses the disease to varying degrees and is called a manifesting carrier.

ABMGG - American Board of Medical Genetics and Genomics Practice Test

ABMGG - American Board of Medical Genetics and Genomics Practice Test

ABMGG ABMGG Inheritance Patterns and Population Genetics