Biochemistry Practice Questions 2

  1. Which of the following is the mRNA start codon in most cases?
  1. UAA
  2. AGU
  3. AUG
  4. UGA
Show Answer
The correct answer is C!

AUG is the canonical start codon. It codes for methionine (formyl-methionine in prokaryotes). UAA and UGA are stop codons.

 

  1. Which type of RNA is the smallest?
  1. mRNA
  2. tRNA
  3. rRNA
  4. DNA
Show Answer
The correct answer is B!

tRNA molecules are about 75–90 nucleotides long. mRNAs vary widely and are often larger, and rRNAs include large species such as 16S and 28S.

 

  1. Which of the following is NOT considered a pyrimidine?
  1. C
  2. T
  3. U
  4. G
Show Answer
The correct answer is D!

Cytosine, thymine, and uracil are pyrimidines (single ring). Guanine is a purine (double ring).

 

  1. Which of the following is paired correctly in double-stranded DNA?
  1. A-G
  2. C-G
  3. A-U
  4. G-T
Show Answer
The correct answer is B!

In DNA, the standard base pairs are A–T and C–G. A–U occurs in RNA.

 

  1. Which of the following characterizes a western blot?
  1. Antibody/protein hybridization
  2. DNA/RNA combination
  3. RNA transcription
  4. Polymerase chain reaction
Show Answer
The correct answer is A!

Western blots detect specific proteins: proteins are separated by SDS-PAGE, transferred to a membrane, and probed with antibodies.

 

  1. Which of the following is the approximate prevalence ratio for cystic fibrosis in people of Northern European descent?
  1. 1:25,000
  2. 1:5,000
  3. 1:2,500
  4. 1:800
Show Answer
The correct answer is C!

Cystic fibrosis occurs in about 1 in 2,500 births among people of Northern European ancestry. The overall US prevalence is about 1 in 3,200.

 

  1. Which of the following divisions of cell growth precedes mitosis in the cell cycle?
  1. G2
  2. G1
  3. S
  4. G0
Show Answer
The correct answer is A!

G2 follows DNA replication (S phase) and immediately precedes mitosis (M phase).

 

  1. Down syndrome is directly linked to a genetic abnormality of which chromosome?
  1. XXII
  2. XXI
  3. XVIII
  4. XV
Show Answer
The correct answer is B!

Down syndrome is trisomy of chromosome 21 (XXI).

 

  1. Which of the following is a characteristic of the Hardy–Weinberg law?
  1. Mating between species occurs at a set rate.
  2. Migration is a considerable factor.
  3. Mutation occurs at the locus.
  4. Genotype selection does not occur at the locus.
Show Answer
The correct answer is D!

Hardy–Weinberg equilibrium assumes no selection, no mutation, no migration, random mating, and a very large population.

 

  1. Which of the following is NOT a characteristic of Hurler syndrome?
  1. Autosomal recessive condition
  2. Associated with delayed mental development
  3. Spasticity
  4. Corneal deficits
Show Answer
The correct answer is C!

Hurler syndrome (MPS I) is autosomal recessive with developmental delay and corneal clouding. Spasticity is not a defining feature.

 

  1. Which of the following is NOT a characteristic of Krabbe disease?
  1. Autosomal recessive condition
  2. Spasticity
  3. Nausea
  4. Optic nerve deficits
Show Answer
The correct answer is C!

Krabbe disease (galactocerebrosidase deficiency) is autosomal recessive with neurodegeneration, spasticity, peripheral neuropathy, and optic atrophy. Nausea is not typical.

 

  1. Which of the following is NOT a characteristic of Fabry disease?
  1. X-linked disease
  2. Low levels of α-galactosidase A
  3. Profound muscular weakness
  4. Increased levels of ceramide trihexoside
Show Answer
The correct answer is C!

Fabry disease is X-linked with deficient α-galactosidase A and accumulation of ceramide trihexoside. Severe muscle weakness is not a hallmark feature.

 

  1. Which of the following is NOT a characteristic of sickle cell anemia?
  1. More common in African Americans
  2. Autosomal dominant
  3. Mutation in β-globin
  4. Intense chronic pain
Show Answer
The correct answer is B!

Sickle cell disease is autosomal recessive, caused by a β-globin point mutation (Glu→Val), and characterized by vaso-occlusive pain crises.

 

  1. Which of the following is NOT a characteristic of the Southern blot?
  1. DNA hybridization
  2. Use of a filter and film combination
  3. Activated by antigen/antibody reactions
  4. Uses a DNA sample
Show Answer
The correct answer is C!

Southern blots analyze DNA via probe hybridization on a membrane. Antigen–antibody reactions are the basis of the western blot.

 

  1. Which of the following is NOT a characteristic of S-adenosyl methionine?
  1. Participates in creatine synthesis (precursor of phosphocreatine)
  2. Considered a rate-limiting enzyme of glycolysis
  3. Aids in the transfer of methyl
  4. Byproduct of methionine and ATP combination
Show Answer
The correct answer is B!

S-adenosyl methionine is a universal methyl donor formed from methionine and ATP. It contributes to creatine synthesis. The rate-limiting enzyme of glycolysis is phosphofructokinase-1, not SAM.

 

  1. Which of the following is NOT an activated carrier?
  1. ATP
  2. SAM
  3. TPP
  4. GMP
Show Answer
The correct answer is D!

Activated carriers include ATP for phosphate, SAM for methyl groups, and TPP for aldehyde transfers. GMP is not typically used as an activated carrier.

 

  1. Per turn of the TCA cycle, how many NADH are produced?
  1. 3
  2. 4
  3. 5
  4. 6
Show Answer
The correct answer is A!

Each cycle yields three NADH from isocitrate dehydrogenase, α-ketoglutarate dehydrogenase, and malate dehydrogenase, plus one FADH2 and one GTP.

 

  1. How many ATP equivalents are required to convert two pyruvate to one glucose via gluconeogenesis?
  1. 5
  2. 6
  3. 7
  4. 8
Show Answer
The correct answer is B!

Gluconeogenesis consumes four ATP and two GTP, totaling six high-energy phosphate equivalents (and two NADH).

 

  1. Which of the following is NOT a derivative of tryptophan?
  1. Melatonin
  2. Serotonin
  3. Creatine
  4. Niacin
Show Answer
The correct answer is C!

Creatine is synthesized from arginine, glycine, and S-adenosyl methionine. Tryptophan gives rise to serotonin, melatonin, and niacin.

 

  1. Pompe disease is a type ___ glycogen storage disease.
  1. I
  2. II
  3. III
  4. IV
Show Answer
The correct answer is B!

Type II (Pompe) is due to acid α-glucosidase deficiency. The classic infantile form presents with cardiomegaly and hypotonia.