CGC Molecular Genetics & Mechanisms of Inheritance

Question 1

Which type of mutation involves the insertion of one or two nucleotides, causing a shift in the reading frame of downstream codons?

Accepted Answer

Frameshift mutation

Answer

Missense mutation

Answer

Nonsense mutation

Answer

Silent mutation

Question 2

Which DNA repair mechanism corrects single-strand mismatches introduced during replication and is defective in Lynch syndrome?

Accepted Answer

Mismatch repair

Answer

Nucleotide excision repair

Answer

Base excision repair

Answer

Homologous recombination

Question 3

What term describes the phenomenon where the expression of a gene depends on whether it was inherited from the mother or the father?

Accepted Answer

Genomic imprinting

Answer

Variable expressivity

Answer

Anticipation

Answer

Incomplete penetrance

Question 4

During meiosis I, homologous chromosomes exchange segments in a process called:

Accepted Answer

Crossing over (recombination)

Answer

Non-disjunction

Answer

Independent assortment

Answer

Sister chromatid exchange

Question 5

Which of the following best describes a de novo mutation?

Accepted Answer

A mutation that arises newly in the affected individual and is not present in either parent

Answer

A mutation inherited from a carrier parent

Answer

A mutation present in all somatic cells but absent from germline

Answer

A mutation that reverts to the wild-type sequence

Question 6

In the context of trinucleotide repeat expansion disorders, which mechanism best explains the phenomenon of anticipation?

Accepted Answer

Repeat sequences become unstable and tend to expand further with each successive transmission

Answer

Increased penetrance in successive generations due to environmental factors

Answer

Epigenetic silencing accumulates over generations reducing gene expression

Answer

Somatic mosaicism increases in severity with each generation

Question 7

Which of the following epigenetic modifications most directly contributes to gene silencing by adding a chemical group to cytosine residues in CpG islands?

Accepted Answer

DNA methylation

Answer

Histone acetylation

Answer

Histone phosphorylation

Answer

Chromatin remodeling via SWI/SNF