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

A frameshift mutation results from insertion or deletion of nucleotides in a number not divisible by three, altering every codon downstream of the 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

Mismatch repair (MMR) corrects replication errors; germline mutations in MMR genes (MLH1, MSH2, MSH6, PMS2) cause Lynch syndrome.

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

Genomic imprinting is an epigenetic process by which gene expression is determined by the parental origin of the allele.

Question 4

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

Accepted Answer

Crossing over (recombination)

Answer

Crossing over (recombination) occurs during prophase I of meiosis when homologous chromosomes exchange corresponding segments, generating genetic diversity.

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 de novo mutation arises spontaneously in the proband and is not inherited from either parent, often explaining isolated cases of dominant disorders.

CGC - Certified Genetic Counselor Practice Test

CGC - Certified Genetic Counselor Practice Test

CGC Molecular Genetics & Mechanisms of Inheritance