EXAM 3 ASU BIO QUESTIONS AND CORRECT
ANSWERS (VERIFIED ANSWERS) PLUS RATIONALES
Q &A 2026 |INSTANT DOWNLOAD PDF
1. Which of the following best describes the role of mRNA in
protein synthesis?
A. Carries amino acids to the ribosome
B. Forms the ribosome itself
C. Conveys genetic information from DNA to the ribosome
D. Acts as an enzyme to link amino acids
Rationale: mRNA is transcribed from DNA and carries the
instructions for assembling a protein at the ribosome.
2. In Mendelian inheritance, what is the expected phenotypic
ratio in the F2 generation of a monohybrid cross?
A. 1:1
B. 3:1
C. 9:3:3:1
D. 1:2:1
Rationale: A monohybrid cross of two heterozygotes (Aa x Aa)
yields 3 dominant:1 recessive phenotype.
3. Which of the following is a product of glycolysis?
,A. Pyruvate
B. Acetyl-CoA
C. Oxaloacetate
D. NADP+
Rationale: Glycolysis converts glucose into pyruvate, producing
a small amount of ATP and NADH.
4. Which type of selection favors the average phenotype and
reduces extremes?
A. Directional
B. Disruptive
C. Stabilizing
D. Sexual
Rationale: Stabilizing selection reduces variation and favors the
intermediate phenotype.
5. Which organelle is primarily responsible for ATP
production?
A. Nucleus
B. Ribosome
C. Lysosome
D. Mitochondrion
Rationale: Mitochondria generate ATP through oxidative
phosphorylation.
,6. What is the main difference between DNA and RNA?
A. DNA contains uracil, RNA contains thymine
B. DNA is single-stranded, RNA is double-stranded
C. DNA contains deoxyribose, RNA contains ribose
D. DNA leaves the nucleus, RNA stays
Rationale: DNA has deoxyribose sugar; RNA has ribose. DNA is
usually double-stranded; RNA is usually single-stranded.
7. Which of the following demonstrates codominance?
A. Red flower x white flower → pink flower
B. AB blood type expressing both A and B alleles equally
C. Tall x short plant → all tall
D. A trait controlled by multiple genes
Rationale: Codominance occurs when both alleles are fully
expressed in the heterozygote.
8. Which type of bond holds amino acids together in a
protein?
A. Hydrogen bond
B. Ionic bond
C. Peptide bond
D. Disulfide bond
, Rationale: Peptide bonds are covalent bonds between the
amino group of one amino acid and the carboxyl group of
another.
9. Which of the following best describes natural selection?
A. Individuals evolve within their lifetime
B. Traits are acquired and passed on
C. Differential survival and reproduction of individuals due to
inherited traits
D. Random changes in allele frequencies
Rationale: Natural selection is a non-random process where
heritable traits that confer a fitness advantage become more
common.
10. What is the primary function of tRNA during translation?
A. Copies DNA
B. Transfers specific amino acids to the ribosome
C. Synthesizes mRNA
D. Acts as a ribozyme
Rationale: tRNA carries amino acids corresponding to the
codons on mRNA and helps build the polypeptide chain.
11. Which of the following occurs during the S phase of the
cell cycle?
ANSWERS (VERIFIED ANSWERS) PLUS RATIONALES
Q &A 2026 |INSTANT DOWNLOAD PDF
1. Which of the following best describes the role of mRNA in
protein synthesis?
A. Carries amino acids to the ribosome
B. Forms the ribosome itself
C. Conveys genetic information from DNA to the ribosome
D. Acts as an enzyme to link amino acids
Rationale: mRNA is transcribed from DNA and carries the
instructions for assembling a protein at the ribosome.
2. In Mendelian inheritance, what is the expected phenotypic
ratio in the F2 generation of a monohybrid cross?
A. 1:1
B. 3:1
C. 9:3:3:1
D. 1:2:1
Rationale: A monohybrid cross of two heterozygotes (Aa x Aa)
yields 3 dominant:1 recessive phenotype.
3. Which of the following is a product of glycolysis?
,A. Pyruvate
B. Acetyl-CoA
C. Oxaloacetate
D. NADP+
Rationale: Glycolysis converts glucose into pyruvate, producing
a small amount of ATP and NADH.
4. Which type of selection favors the average phenotype and
reduces extremes?
A. Directional
B. Disruptive
C. Stabilizing
D. Sexual
Rationale: Stabilizing selection reduces variation and favors the
intermediate phenotype.
5. Which organelle is primarily responsible for ATP
production?
A. Nucleus
B. Ribosome
C. Lysosome
D. Mitochondrion
Rationale: Mitochondria generate ATP through oxidative
phosphorylation.
,6. What is the main difference between DNA and RNA?
A. DNA contains uracil, RNA contains thymine
B. DNA is single-stranded, RNA is double-stranded
C. DNA contains deoxyribose, RNA contains ribose
D. DNA leaves the nucleus, RNA stays
Rationale: DNA has deoxyribose sugar; RNA has ribose. DNA is
usually double-stranded; RNA is usually single-stranded.
7. Which of the following demonstrates codominance?
A. Red flower x white flower → pink flower
B. AB blood type expressing both A and B alleles equally
C. Tall x short plant → all tall
D. A trait controlled by multiple genes
Rationale: Codominance occurs when both alleles are fully
expressed in the heterozygote.
8. Which type of bond holds amino acids together in a
protein?
A. Hydrogen bond
B. Ionic bond
C. Peptide bond
D. Disulfide bond
, Rationale: Peptide bonds are covalent bonds between the
amino group of one amino acid and the carboxyl group of
another.
9. Which of the following best describes natural selection?
A. Individuals evolve within their lifetime
B. Traits are acquired and passed on
C. Differential survival and reproduction of individuals due to
inherited traits
D. Random changes in allele frequencies
Rationale: Natural selection is a non-random process where
heritable traits that confer a fitness advantage become more
common.
10. What is the primary function of tRNA during translation?
A. Copies DNA
B. Transfers specific amino acids to the ribosome
C. Synthesizes mRNA
D. Acts as a ribozyme
Rationale: tRNA carries amino acids corresponding to the
codons on mRNA and helps build the polypeptide chain.
11. Which of the following occurs during the S phase of the
cell cycle?
