Question 1

Which of the following best describes autosomal dominant (AD) inheritance?

Accepted Answer

A clinical phenotype is expressed when only one mutant allele is present.

Question 2

A man with an autosomal dominant disease (heterozygous, genotype $$Hh) $$has children with a woman who is unaffected (genotype $$hh). $$What is the probability that their child will be affected?

Accepted Answer

$$50\%$$

Question 3

Which of the following is a key feature of autosomal dominant inheritance patterns in pedigrees?

Accepted Answer

The phenotype appears in every generation unless there is reduced penetrance.

Question 4

Which of the following diseases is NOT typically inherited in an autosomal dominant manner?

Accepted Answer

Cystic Fibrosis

Question 5

A couple, both heterozygous for an autosomal dominant disorder ($$Hh$$), have a child. What is the probability that the child will be homozygous for the mutant allele ($$HH$$)?

Accepted Answer

$$1/4$$

Question 6

Which of the following best explains why many autosomal dominant diseases are due to mutations in genes coding for non-enzymatic structural proteins?

Accepted Answer

Structural proteins often function as complexes, so a single mutant allele can disrupt the entire complex.

Question 7

In a pedigree, an autosomal dominant disease appears in every generation, but one individual with the mutant genotype does not show symptoms. What is the most likely explanation?

Accepted Answer

Incomplete penetrance

Question 8

Which of the following statements about de novo mutations in autosomal dominant diseases is correct?

Accepted Answer

De novo mutations can cause a disease in a child even if neither parent is affected.

Question 9

A pedigree shows a disease affecting both males and females in every generation, with approximately half the children of an affected parent being affected. Which inheritance pattern is most likely?

Accepted Answer

Autosomal dominant

Question 10

Which of the following best describes 'variable expressivity' in autosomal dominant diseases?

Accepted Answer

Different individuals with the same genotype show different severity of symptoms.

Question 11

If two individuals with a complete autosomal dominant disease ($$Hh) $$have children, what is the expected phenotypic ratio among their offspring?

Accepted Answer

$$3$$ affected : $$1$$ unaffected

Question 12

Which of the following is an example of a disease with autosomal dominant inheritance that is common in certain populations?

Accepted Answer

Myotonic Dystrophy in Quebec

Question 13

A child is born to an unaffected mother and a father with Huntington disease (heterozygous). What is the probability that the child will inherit the mutant allele?

Accepted Answer

$$50\%$$

Question 14

Which of the following best distinguishes complete from incomplete autosomal dominant inheritance?

Accepted Answer

In complete dominance, heterozygotes and homozygotes have the same phenotype; in incomplete dominance, heterozygotes have an intermediate phenotype.

Question 15

Which of the following is a likely outcome if both parents are homozygous for a mutant allele causing a complete autosomal dominant disease ($$HH$$)?

Accepted Answer

All children will be affected and homozygous for the mutant allele.

Question 16

In autosomal dominant inheritance, what is the risk that an unaffected child of an affected ($$Hh) $$and unaffected ($$hh) $$parent will have an affected child if they marry an unaffected partner?

Accepted Answer

$$0\%$$

Question 17

Which of the following best explains why autosomal dominant diseases are often seen in every generation of a pedigree?

Accepted Answer

Only one mutant allele is needed for the phenotype to be expressed.

Question 18

A pedigree shows a disease affecting both sexes equally, with affected individuals in every generation. However, one generation has no affected individuals. What is a possible explanation?

Accepted Answer

Reduced penetrance

Question 19

Which of the following statements about the risk of recurrence in autosomal dominant inheritance is correct?

Accepted Answer

The risk of having an affected child is independent of the genotype/phenotype of previous children.

Autosomal Dominant Inheritance: Principles and Examples

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