Deck 7: Patterns of Single-Gene Inheritance

Question 1

What degree of relationship to each other are half-siblings?

A) First
B) Second
C) Third
D) Fourth
E) Fifth

Answer 1

Second

Question 2

If an uncle has children with his niece, which of the following genetic terms is used to describe this relationship?

A) Interrelatedness
B) Recessivity
C) Inbreeding loop
D) Pedigree inversion
E) Consanguinity

Answer 2

Consanguinity

Question 3

What is the term used to describe the patient who first brings a family to a geneticist's attention?

A) Consultand
B) Primary case
C) Proband
D) Referral case
E) Any of the above

Answer 3

Proband

Question 4

Which of the following is a likely explanation that a male could survive an X-linked dominant, male lethal disorder?

A) He could have a mutation reversion
B) He could have a compensating mutation
C) He could be 47, XXY
D) There is recombination between the X and Y chromosome
E) Any of the above is likely

Question 5

In certain proteins, expansion of a tract of which amino acid is associated with various genetic forms of progressive neurodegeneration?

A) Alanine
B) Proline
C) Valine
D) Methionine
E) Glutamine

Question 6

Which of the following terms refers to the fact that different people with the same genotype can have variation in phenotype?

A) Reduced penetrance
B) Variable expressivity
C) Incomplete dominance
D) Codominance
E) Allelic heterogeneity

Question 7

Trinucleotide repeat alleles that are not associated with the disease phenotype but that can expand during meiosis are known as:

A) Permutations
B) Pseudo-disease alleles
C) Pre-expansions
D) Expansion-prone alleles
E) Unstable alleles

Question 8

For an autosomal dominant disease, if two affected parents have a child, what is most likely the risk of passing on the disorder?

A) 0
B) 25%
C) 50%
D) 75%
E) 100%

Question 9

Which of the following are true about mitochondrial inheritance?

A) There is heteroplasmy
B) The mitochondria segregate randomly as cells divide
C) Mitochondria are maternally inherited
D) There are approximately 1000 mitochondrial DNA (mtDNA) molecules per cell
E) All of the above

Question 10

A process that can greatly affect the presentation of an X-linked phenotype in carrier females is:

A) Interfering mutations
B) X-inactivation
C) Mitochondrial expression
D) Recombination between X homologues
E) Mutation repair between homologues

Question 11

Which of the following terms refers to a set of alleles that is inherited together on a chromosome?

A) Linkage disequilibrium
B) Chromatid
C) Haplotype
D) Epistatic alleles
E) Genotype

Question 12

Unstable trinucleotide repeat alleles can be observed to expand in which of the following situations?

A) During meiosis in a male premutation carrier
B) During meiosis in a female premutation carrier
C) During mitosis in an individual with a disease allele
D) Both A and B
E) Both B and C

Question 13

Genetic anticipation is associated with:

A) More mutated mitochondria being passed from the mother in later generations
B) An increased age of onset in later generations
C) Toxic metabolites being passed to the fetus in an affected mother
D) Trinucleotide repeat instability
E) Threshold of expression of mutations

Question 14

When a set of parents has a child affected by an autosomal recessive disorder, the most likely recurrence risk is:

A) 100%
B) 50%
C) 33%
D) 25%
E) 12.5%

Question 15

What genetic force leads to the variability in the percentage of mutant mtDNA molecules that are present in the children of a mother who exhibits heteroplasmy for the mutation?

A) Positive selection
B) Negative selection
C) Genetic bottleneck
D) Reduced fitness
E) Balancing selection

Question 16

What is the most likely explanation for a set of unaffected parents having two children with a highly-penetrant, autosomal dominant disorder?

A) Two new mutations occurred in the same gene
B) Germline mosaicism in one of the parents
C) Variable expressivity
D) Somatic reversion in carrier parent
E) Inactivation of mutant allele in carrier parent

Question 17

Which type of mitochondrial mutation is NOT passed from an affected mother to her child when the mother exhibits heteroplasmy for the mutation?

A) Deletion
B) Duplication
C) Missense mutation
D) Nonsense mutation
E) Repeat expansion

Question 18

What is the risk for hemophilia A in the grandsons if their paternal grandfather is a hemophiliac?

A) 0
B) 1/8
C) 1/4
D) 1/2
E) 100%

Question 19

Anticipation is the finding in a genetic disorder that:

A) Mutations in the promoter are more severe than those in exons
B) One is more likely to diagnose genetic disease in additional family members once a family is referred for genetic counseling
C) The severity of phenotype increases, and age of onset decreases as some genetic disorders are passed through families
D) The known variability in a disease phenotype increases once a disorder is described in the literature because of better clinical observation
E) For many complex traits, the likelihood of having an affected child increases the risk of having a second affected child

Question 20

Heteroplasmy is associated with:

A) Difficulty in making a prenatal diagnosis
B) Random inactivation of the X chromosome
C) Repeat instability
D) Increased severity in later generations
E) All of the above