Question 1

A patient is heterozygous for a gene that encodes a multimeric protein. One allele is wild-type, and the other is a mutant that produces a nonfunctional subunit that interferes with the function of the wild-type protein. What type of mutation is this most likely to be?

Accepted Answer

A dominant negative (antimorph) mutation

Question 2

A nonsense mutation occurs at the second codon of a gene that normally encodes a 200-amino acid protein. Which term best describes the resulting allele?

Accepted Answer

Null/amorphic

Question 3

A woman with a single harmful BRCA1 mutation has a 60% chance of developing breast cancer by age 70. What does this indicate about the BRCA1 mutation?

Accepted Answer

It is incompletely penetrant

Question 4

A child is diagnosed with phenylketonuria (PKU), an autosomal recessive disorder. Which of the following best explains why a strict diet can prevent the symptoms of PKU?

Accepted Answer

The diet reduces the intake of phenylalanine, preventing toxic buildup

Question 5

In the context of the ABO blood group system, which genotype results in the expression of both A and B antigens on the surface of red blood cells?

Accepted Answer

$$I^A I^B$$

Question 6

A cross between two yellow mice (genotype $$A^Y A) $$produces offspring in a 2:1 ratio of yellow to agouti. What is the most likely explanation for this result?

Accepted Answer

The $$A^Y$$ allele is a recessive lethal

Question 7

A patient with Marfan syndrome has a mutation in the fibrillin gene that disrupts the formation of microfibrils, even in the presence of a normal allele. What type of mutation is this?

Accepted Answer

Dominant negative (antimorph)

Question 8

Which of the following best describes the inheritance pattern of a gene that is recessive for disease presence, co-dominant for protein production, and incompletely dominant for oxygen carrying capacity, as seen in sickle cell anemia?

Accepted Answer

The gene shows multiple types of dominance depending on the phenotype measured

Question 9

A pedigree shows an autosomal dominant trait where not all individuals with the mutant allele express the phenotype. What is this phenomenon called?

Accepted Answer

Incomplete penetrance

Question 10

A gene mutation causes a protein to be expressed in tissues where it is not normally found, resulting in a new function. What type of mutation is this?

Accepted Answer

Neomorphic

Question 11

A flower with genotype $$C^R C^W$$ produces pink petals, while $$C^R C^R is $$red and $$C^W C^W is $$white. What type of inheritance is this?

Accepted Answer

Incomplete dominance

Question 12

A person with Waardenburg syndrome may have hearing loss, different-colored eyes, and a white forelock, but not all symptoms are present in every affected individual. What genetic concept does this illustrate?

Accepted Answer

Variable expressivity

Question 13

A gene is described as haploinsufficient. What does this mean?

Accepted Answer

One wild-type allele is not enough for a normal phenotype

Question 14

Which of the following best describes pleiotropy?

Accepted Answer

A single gene affects multiple phenotypic traits

Question 15

A child with cystic fibrosis has thick mucus in the lungs, blocked pancreatic ducts, and salty sweat. Which genetic concept does this illustrate?

Accepted Answer

Pleiotropy

Question 16

A gene's expression is silenced by methylation, and this silencing is inherited for several generations. What is this phenomenon called?

Accepted Answer

Epigenetics

Question 17

A person with genotype $$I^A i$$ for the ABO blood group has which blood type?

Accepted Answer

Type A

Question 18

A mutation in the telomerase gene causes dyskeratosis congenita, where one wild-type allele is not sufficient to maintain telomere length. What is this an example of?

Accepted Answer

Haploinsufficiency

Question 19

A person with the genotype $$ii$$ for the ABO blood group system will have which phenotype?

Accepted Answer

Type O blood

Question 20

A gene mutation results in a protein with increased activity compared to the wild-type. What is this type of mutation called?

Accepted Answer

Hypermorphic

Beyond Mendelian Genetics: Extensions and Complexities in Allelic Interactions

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