13 USMLE Pathology, Hematology and Genetics Quick Review Questions with Answers (Set 3)

These 13 quick USMLE review questions test high-yield facts that show up again and again on the exam: collagen, sickle cell selection, Niemann-Pick disease, p53, DiGeorge syndrome, G6PD, gene therapy, muscle enzymes, Gilbert syndrome, vitamin B12 deficiency and hCG. Each question includes the correct answer.

Written by Dr. Ray Makar, MD, author of the Repeated USMLE Questions eBook series.

Prefer video? Watch daily USMLE case questions on MedFocus by Dr. Ray on YouTube.

How to use this page: read the question, pick your answer, then tap Show Answer and Explanation.

Questions

Question 1. Measurement of the content of which one of the following could help to compare the collagen content of several tissues?

A- Cysteine
B- Glycine
C- Hydroxyproline
D- Proline

C- Hydroxyproline- Although collagen is rich in glycine, several tissues also contain significant amounts of glycine. Hydroxyproline is found uniquely in collagen.
The correct answer is C

 

Question 2. Which of the following explains the higher incidence of sickle cell disease in African Americans more than other races?

A- Genetic drift
B- Increased gene flow
C- Increased mutation rate
D- Natural selection

D- Natural selection- Heterozygous carriers are resistant to malarial infection but at the same time they don’t develop sickle cell disease because it is autosomal recessive. There is selective advantage for this mutation elevating its incidence in this population.
The correct answer is D

 

Question 3. Niemann-Pick disease is characterized by deficiency of which one of the following enzymes?

A- Alpha-glucosidase
B- Arylsulfatase
C- Beta-glucosidase
D- Sphingomyelinase

D- Sphingomyelinase- This disease affects infants in the first year of life leading to mental retardation and hepatosplenomegaly.
The correct answer is D

 

Question 4. Which of the following types of protein is encoded by the P53 gene?

A- Caspase
B- DNA repair enzyme
C- Transcription factor
D- Tyrosine kinase

C- Transcription factor- P53 is a transcription factor regulates apoptosis. It prevents cells from undergoing division. Mutation in it causes uncontrolled cell division.
The correct answer is C

 

Question 5. A newborn infant presents with cleft palate and hypocalcemia. Genetic testing of the blood shows a 22q11.2 deletion. Which of the following is the most likely diagnosis?

A- DiGeorge Syndrome
B- Down syndrome
C- Stickler syndrome
D- Turner’s syndrome

A- DiGeorge Syndrome- is the only one of the list that has this deletion and characterized by cleft palate, hypoparathyroidism and low CD4.
The correct answer is A

 

Question 6. Which of the following is the mode of inheritance of glucose-6-phosphate dehydrogenase deficiency?

A- Autosomal dominant
B- Autosomal recessive
C- X-linked dominant
D- X-linked recessive

D- X-linked recessive- It leads to hemolytic anemia after taking certain food and medications.
The correct answer is D

 

Question 7. A patient with cystic fibrosis is treated by gene therapy. Which of the following types of cells should be targeted as host cells?

A- Epithelial cells
B- Hemopoietic stem cells
C- Germ cells
D- T-cells

A- Epithelial cells- Chloride transport is defected in these cells.
The correct answer is A

 

Question 8. Which one of the following enzymes is extremely important in muscle energy metabolism through its role in purine nucleotide cycle?

A- Adenosine deaminase
B- Hypoxanthine-guanine phosphoribosyltransferase (HGPRT)
C- Myoadenylate deaminase
D- Myo-inositol monophosphatase

C- Myoadenylate deaminase- It catalyses the deamination of AMP to IMP which is important step in purine nucleotide metabolism.
The correct answer is C

 

Question 9. Gilbert syndrome may manifest only as jaundice. 30% of patients are asymptomatic. Which of the following findings is most likely in a patient with Gilbert syndrome?

A- Decreased activity of UDP glucuronosyltransferase
B- Decreased serum unconjugated bilirubin
C- Increased activity of alkaline phosphatase
D- Increased formation of gall stones

A- Decreased activity of UDP glucuronosyltransferase- Gilbert syndrome is characterized by intermittent hyperbilirubinemia which results in intermittent jaundice due to decreased glucuronidation of bilirubin.
The correct answer is A

 

Question 10. A 34-year-old woman presents with weakness, easy fatigability and numbness and tingling of her arms and legs. CBC reveals pancytopenia and marked increase in the MCV of erythrocytes. More investigations reveal chronic atrophic gastritis. What is the most likely diagnosis?

A- Aplastic anemia
B- Folic acid deficiency anemia
C- Iron deficiency anemia
D- Vitamin B12 deficiency

D- Vitamin B12 deficiency- This is a typical case of vitamin B12 deficiency macrocytic anemia due to lack of intrinsic factor results from gastric atrophy. Intrinsic factor is essential for Vitamin B12 abortion.
The correct answer is D

 

Question 11. Which one of the following conditions is NOT a common cause of vitamin B12 deficiency?

A- Diet deficiency of vitamin B12
B- Gastric bypass
C- Intrinsic factor deficiency
D- Malabsorption syndrome

A- Diet deficiency of vitamin B12- This deficiency is very rare although it is starting to be seen due to aggressive vegan diet but it is still not as common as other choices.
The correct answer is A

 

Question 12. Which of the following substances is elevated due to vitamin B12 deficiency?

A- Cyanocobalamin
B- Folic acid
C- Homocysteine
D- Hemosiderin

C- Homocysteine- It is elevated as well as methylmalonic acid due to deficiency of vitamin B12 which is involved in the conversion of homocysteine to methionine. Cyanocobalamin is a different name of vitamin B12 and folic acid deficiency leads to macrocytic anemia, not high levels. Hemosiderin is involved in hemochromatosis and some other medical conditions.
The correct answer is C

 

Question 13. A patient presents with painless scrotal mass and increased thyroid panel. Which of the following markers would be elevated in this patient?

A- Alpha-fetoprotein
B- Follicle stimulating hormone
C- Human chorionic gonadotropin
D- Lactate dehydrogenase

C- Human chorionic gonadotropin- alpha subunits of HCG and TSH are identical so, circulating HCG in large amounts stimulates the thyroid gland secretion leading to paraneoplastic hyperthyroidism.
The correct answer is C

 

High-yield points from this set

  • Niemann-Pick disease = sphingomyelinase deficiency.
  • p53 is a transcription factor (tumor suppressor).
  • Gilbert syndrome = mildly decreased UDP-glucuronosyltransferase.
  • Vitamin B12 deficiency raises homocysteine and methylmalonic acid.

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