Molecular Genetics Practice Questions

Question 1

A researcher is investigating compounds that modulate the cell cycle as possible chemotherapeutic agents against peripheral T-cell lymphoma. The researcher discovers a group of natural compounds with inhibitory activity against histone deacetylases, a class of enzymes that remove acetyl groups from the lysine residues of histones. A histone deacetylase inhibitor most likely causes which of the following?

Accepted Answer

Relaxation of DNA coiling

Answer

Prevention of DNA strand reannealing

Answer

Increased heterochromatin formation

Answer

Suppression of gene transcription

Answer

Tighter coiling of DNA

Question 2

A 25-year-old man with a genetic disorder presents for genetic counseling because he is concerned about the risk that any children he has will have the same disease as himself. Specifically, since childhood he has had difficulty breathing requiring bronchodilators, inhaled corticosteroids, and chest physiotherapy. He has also had diarrhea and malabsorption requiring enzyme replacement therapy. If his wife comes from a population where 1 in 10,000 people are affected by this same disorder, which of the following best represents the likelihood a child would be affected as well?

Accepted Answer

1%

Answer

0.01%

Answer

2%

Answer

0.5%

Answer

50%

Question 3

A 71-year-old man with colorectal cancer comes to the physician for follow-up examination after undergoing a sigmoid colectomy. The physician recommends adjuvant chemotherapy with an agent that results in single-stranded DNA breaks. This chemotherapeutic agent most likely has an effect on which of the following enzymes?

Accepted Answer

Topoisomerase I

Answer

DNA polymerase III

Answer

Helicase

Answer

Telomerase

Answer

Topoisomerase II

Question 4

An investigator is studying the biology of human sperm cells. She isolates spermatogonia obtained on a testicular biopsy from a group of healthy male volunteers. She finds that the DNA of spermatogonia obtained from these men show a large number of TTAGGG sequence repeats. This finding can best be explained by increased activity of an enzyme with which of the following functions?

Accepted Answer

RNA-dependent synthesis of DNA

Answer

Ligation of Okazaki fragments

Answer

Proofreading of synthesized daughter strands

Answer

Production of short RNA sequences

Answer

Hemimethylation of DNA strand

Question 5

A 30-year-old man presents to his primary care physician for a routine check-up. During the appointment, he remarks that he has started noticing some thinning and hair loss without other symptoms. The physician reassures him that he is likely experiencing male-pattern baldness and explains that the condition is largely inherited. Specifically he notes that there are multiple genes that are responsible for the condition so it is difficult to predict the timing and development of hair loss. What genetic principle is being illustrated by this scenario?

Accepted Answer

Polygenic inheritance

Answer

Uniparental disomy

Answer

Pleiotropy

Answer

Anticipation

Answer

Heteroplasmy

Question 6

A group of researchers is studying molecules and DNA segments that are critical for important cellular processes in eukaryotic cells. They have identified a region that is located about 28 bases upstream of the 5’ coding region. This region promotes the initiation of transcription by binding with transcription factors. Which of the following regions have these researchers most likely identified?

Accepted Answer

TATA Box

Answer

RNA polymerase II

Answer

Small nuclear ribonucleoprotein (SnRNPs)

Answer

DNA methyltransferase

Answer

CAAT Box

Question 7

A 31-year-old man and his wife were referred to a genetic counselor. They are concerned about the chance that their children are likely to inherit certain conditions that run in their families. The wife's father and grandfather are both healthy, but her grandfather cannot see the color red. The husband is unaware if any member of his family has the same condition. The geneticist provides some details about genetic diseases and inheritance patterns, then orders lab tests to analyze the gene mutations carried by both partners. Which of the following are the correct terms regarding the genotype and phenotype of males affected by the condition described?

Accepted Answer

Hemizygous; full penetrance

Answer

Homozygote; reduced or incomplete penetrance

Answer

Heterozygotes; reduced or incomplete penetrance

Answer

Hemizygous; reduced or incomplete penetrance

Answer

Heterozygotes; full penetrance

Question 8

An investigator is studying human genetics and cell division. A molecule is used to inhibit the exchange of genetic material between homologous chromosomes. Which of the following phases of the cell cycle does the molecule target?

Accepted Answer

Prophase I

Answer

Prophase II

Answer

Metaphase II

Answer

Telophase I

Answer

Anaphase I

Question 9

A 5-year-old patient presents to the pediatrician's office with fatigue and swollen lymph nodes. Extensive work-up reveals a diagnosis of acute lymphoblastic leukemia. In an effort to better tailor the patient's treatments, thousands of genes are arranged on a chip and a probe is made from the patient's mRNA (converted to cDNA). This probe is then hybridized to the chip in order to measure the gene expression of thousands of genes. The technology used to investigate this patient's gene expression profile is best for detecting which of the following types of genetic abnormalities?

Accepted Answer

Chromosomal translocations

Answer

Trisomies

Answer

Large scale chromosomal deletions

Answer

Frame-shift mutations

Answer

Single nucleotide polymorphisms

Question 10

As part of a clinical research study, the characteristics of neoplastic and normal cells are being analyzed in culture. It is observed that neoplastic cell division is aided by an enzyme which repairs progressive chromosomal shortening, which is not the case in normal cells. Due to the lack of chromosomal shortening, these neoplastic cells divide more rapidly than the normal cells. Which of the following enzymes is most likely involved?

Accepted Answer

Telomerase

Answer

Topoisomerase

Answer

DNA polymerase

Answer

Reverse transcriptase

Answer

Protein kinase

Molecular Genetics

Study Resources

Lessons

Questions

Flashcards

Lessons

DNA structure and organization

Chromosomal structure

DNA replication

Cell cycle and mitosis

Meiosis and genetic recombination

Mutation types and consequences

Mendelian inheritance patterns

Non-Mendelian inheritance

Genetic linkage and mapping

Population genetics principles

Genetic polymorphisms

Gene therapy approaches

Practice Questions

Flashcards

About Molecular Genetics for USMLE

Lessons in Molecular Genetics

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