Genetic polymorphisms — MCQs

An investigator is studying genetic mutations of coagulation factors from patient samples. Genetic sequencing of one patient's coagulation factors shows a DNA point mutation that substitutes guanine for adenine. The corresponding mRNA codon forms a glutamine in place of arginine on position 506 at the polypeptide cleavage site. This patient's disorder is most likely to cause which of the following?

A newlywed couple comes to your office for genetic counseling. Both potential parents are known to be carriers of the same Cystic Fibrosis (CF) mutation. What is the probability that at least one of their next three children will have CF if they are all single births?

An 8-year-old boy is brought to the pediatrician because his mother is concerned about recent behavioral changes. His mother states that she has started to notice that he is slurring his speech and seems to be falling more than normal. On exam, the pediatrician observes the boy has pes cavus, hammer toes, and kyphoscoliosis. Based on these findings, the pediatrician is concerned the child has a trinucleotide repeat disease. Which of the following trinucleotide repeats is this child most likely to possess?

A 58-year-old man comes to the physician because of severe muscle aches and fatigue for 3 days. Last week he was diagnosed with atypical pneumonia and treated with clarithromycin. He has hyperlipidemia for which he takes lovastatin. Physical examination shows generalized tenderness of the proximal muscles in the upper and lower extremities. Serum studies show an elevated creatine kinase concentration. This patient's current symptoms are most likely caused by inhibition of which of the following hepatic enzymes?

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?

A 34-year-old woman, gravida 1, para 0, at 18 weeks' gestation, comes to the physician for a prenatal visit. She recently read about a genetic disorder that manifests with gait ataxia, kyphoscoliosis, and arrhythmia and is concerned about the possibility of her child inheriting the disease. There is no personal or family history of this disorder. The frequency of unaffected carriers in the general population is 1/100. Assuming the population is in a steady state without selection, what is the probability that her child will develop this disease?

A 23-year-old woman and her husband come to a genetic counselor because she is concerned about the chance of having an inherited defect if they had a child. Family history reveals no significant family history in her husband; however, her sister had a son who has seizures, failure to thrive, and neurodegeneration. She does not remember the name of the disease but remembers that her nephew had sparse, brittle hair that kinked in odd directions. She does not think that any other members of her family including her sister's husband have had this disorder. If this couple had a son, what is the most likely chance that he would have the same disorder that affected the patient's nephew?

A healthy 29-year-old nulligravid woman comes to the physician for genetic counseling prior to conception. Her brother has a disease that has resulted in infertility, a right-sided heart, and frequent sinus and ear infections. No other family members are affected. The intended father has no history of this disease. The population prevalence of this disease is 1 in 40,000. Which of the following best represents the chance that this patient’s offspring will develop her brother's disease?

Drug A is an experimental compound being investigated for potential use as a protectant against venous thrombosis. Binding assays reveal that the drug’s primary mechanism of action is to block carboxylation of glutamic acid residues in certain serum proteins. Drug A is most similar to which of the following:

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?