BIO 172 UH EXAM 2 | QUESTIONS AND ANSWERS | VERIFIED
ANSWERS PLUS RATIONALES | EXAM ALREADY GRADED
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1. Which organelle is responsible for producing ATP in the cell?
A. Nucleus
B. Ribosome
C. Mitochondrion
D. Golgi apparatus
Answer: C – The mitochondrion produces ATP through cellular respiration, making it the cell’s
“powerhouse.”
2. During DNA replication, which enzyme is responsible for unwinding the double helix?
A. DNA ligase
B. DNA helicase
C. DNA polymerase
D. RNA polymerase
Answer: B – DNA helicase unwinds the DNA strands to allow replication.
3. What type of bond holds complementary base pairs together in DNA?
A. Ionic bonds
B. Covalent bonds
C. Hydrogen bonds
D. Peptide bonds
Answer: C – Hydrogen bonds form between complementary bases, stabilizing the DNA double
helix.
4. Which phase of mitosis is characterized by chromosomes lining up at the cell’s equator?
A. Prophase
B. Metaphase
C. Anaphase
D. Telophase
Answer: B – During metaphase, chromosomes align at the metaphase plate before being
separated.
5. In Mendelian genetics, what is the expected phenotypic ratio of a monohybrid cross
between two heterozygotes?
,A. 1:1
B. 3:1
C. 2:1
D. 4:0
Answer: B – A cross of Aa × Aa results in a 3:1 dominant to recessive phenotypic ratio.
6. Which macromolecule serves as the main structural component of cell membranes?
A. Proteins
B. Lipids
C. Carbohydrates
D. Nucleic acids
Answer: B – Lipids, primarily phospholipids, form the bilayer structure of cell membranes.
7. What process converts mRNA into a polypeptide chain?
A. Replication
B. Transcription
C. Translation
D. Splicing
Answer: C – Translation is the process of decoding mRNA into a protein.
8. During which phase of the cell cycle does DNA synthesis occur?
A. G1 phase
B. S phase
C. G2 phase
D. M phase
Answer: B – The S phase (synthesis phase) is when DNA is replicated.
9. Which nitrogenous base is unique to RNA and not found in DNA?
A. Adenine
B. Thymine
C. Uracil
D. Cytosine
Answer: C – Uracil replaces thymine in RNA.
10. A cross between two pea plants, one with yellow seeds (YY) and one with green seeds
(yy), will produce offspring with which genotype?
A. YY
B. Yy
C. yy
D. Yy and yy
Answer: B – All offspring will be heterozygous (Yy) and display the dominant yellow phenotype.
,11. Which organelle is responsible for protein synthesis?
A. Lysosome
B. Ribosome
C. Smooth ER
D. Chloroplast
Answer: B – Ribosomes translate mRNA into proteins.
12. In a Punnett square, crossing two heterozygotes for a trait (Aa × Aa) will produce what
genotypic ratio?
A. 1:2:1
B. 3:1
C. 2:1
D. 4:0
Answer: A – The genotypic ratio for Aa × Aa is 1 AA : 2 Aa : 1 aa.
13. What type of RNA carries amino acids to the ribosome?
A. mRNA
B. rRNA
C. tRNA
D. snRNA
Answer: C – Transfer RNA (tRNA) brings amino acids to the ribosome during translation.
14. Which component of the cell membrane acts as a barrier to most water-soluble
substances?
A. Cholesterol
B. Phospholipid bilayer
C. Glycoproteins
D. Cytoskeleton
Answer: B – The hydrophobic interior of the phospholipid bilayer prevents free passage of polar
molecules.
15. During transcription, RNA is synthesized in which direction?
A. 3’ to 5’
B. 5’ to 3’
C. Both directions
D. Randomly
Answer: B – RNA polymerase synthesizes RNA in the 5’ → 3’ direction.
16. Which structure is only found in plant cells and not animal cells?
, A. Nucleus
B. Mitochondria
C. Chloroplast
D. Golgi apparatus
Answer: C – Chloroplasts carry out photosynthesis and are unique to plants.
17. In a dihybrid cross between two heterozygotes (AaBb × AaBb), what is the expected
phenotypic ratio?
A. 9:3:3:1
B. 3:1
C. 1:1
D. 2:1
Answer: A – The classic dihybrid cross results in 9 dominant both : 3 dominant A only : 3
dominant B only : 1 recessive both.
18. Which organelle contains hydrolytic enzymes to digest cellular waste?
A. Lysosome
B. Peroxisome
C. Ribosome
D. Endosome
Answer: A – Lysosomes break down macromolecules and damaged organelles.
19. Which phase of mitosis involves separation of sister chromatids?
A. Prophase
B. Metaphase
C. Anaphase
D. Telophase
Answer: C – Anaphase is when sister chromatids are pulled apart to opposite poles.
20. What is the complementary DNA sequence to 5’-AGTCG-3’?
A. 3’-TCAGC-5’
B. 3’-AGTCG-5’
C. 5’-TCAGC-3’
D. 3’-UCAGC-5’
Answer: A – Complementary bases pair A-T and G-C, forming 3’-TCAGC-5’.
21. Which type of bond connects amino acids in a protein?
A. Hydrogen bond
B. Ionic bond
C. Peptide bond
ANSWERS PLUS RATIONALES | EXAM ALREADY GRADED
A+ | LATEST EXAM
1. Which organelle is responsible for producing ATP in the cell?
A. Nucleus
B. Ribosome
C. Mitochondrion
D. Golgi apparatus
Answer: C – The mitochondrion produces ATP through cellular respiration, making it the cell’s
“powerhouse.”
2. During DNA replication, which enzyme is responsible for unwinding the double helix?
A. DNA ligase
B. DNA helicase
C. DNA polymerase
D. RNA polymerase
Answer: B – DNA helicase unwinds the DNA strands to allow replication.
3. What type of bond holds complementary base pairs together in DNA?
A. Ionic bonds
B. Covalent bonds
C. Hydrogen bonds
D. Peptide bonds
Answer: C – Hydrogen bonds form between complementary bases, stabilizing the DNA double
helix.
4. Which phase of mitosis is characterized by chromosomes lining up at the cell’s equator?
A. Prophase
B. Metaphase
C. Anaphase
D. Telophase
Answer: B – During metaphase, chromosomes align at the metaphase plate before being
separated.
5. In Mendelian genetics, what is the expected phenotypic ratio of a monohybrid cross
between two heterozygotes?
,A. 1:1
B. 3:1
C. 2:1
D. 4:0
Answer: B – A cross of Aa × Aa results in a 3:1 dominant to recessive phenotypic ratio.
6. Which macromolecule serves as the main structural component of cell membranes?
A. Proteins
B. Lipids
C. Carbohydrates
D. Nucleic acids
Answer: B – Lipids, primarily phospholipids, form the bilayer structure of cell membranes.
7. What process converts mRNA into a polypeptide chain?
A. Replication
B. Transcription
C. Translation
D. Splicing
Answer: C – Translation is the process of decoding mRNA into a protein.
8. During which phase of the cell cycle does DNA synthesis occur?
A. G1 phase
B. S phase
C. G2 phase
D. M phase
Answer: B – The S phase (synthesis phase) is when DNA is replicated.
9. Which nitrogenous base is unique to RNA and not found in DNA?
A. Adenine
B. Thymine
C. Uracil
D. Cytosine
Answer: C – Uracil replaces thymine in RNA.
10. A cross between two pea plants, one with yellow seeds (YY) and one with green seeds
(yy), will produce offspring with which genotype?
A. YY
B. Yy
C. yy
D. Yy and yy
Answer: B – All offspring will be heterozygous (Yy) and display the dominant yellow phenotype.
,11. Which organelle is responsible for protein synthesis?
A. Lysosome
B. Ribosome
C. Smooth ER
D. Chloroplast
Answer: B – Ribosomes translate mRNA into proteins.
12. In a Punnett square, crossing two heterozygotes for a trait (Aa × Aa) will produce what
genotypic ratio?
A. 1:2:1
B. 3:1
C. 2:1
D. 4:0
Answer: A – The genotypic ratio for Aa × Aa is 1 AA : 2 Aa : 1 aa.
13. What type of RNA carries amino acids to the ribosome?
A. mRNA
B. rRNA
C. tRNA
D. snRNA
Answer: C – Transfer RNA (tRNA) brings amino acids to the ribosome during translation.
14. Which component of the cell membrane acts as a barrier to most water-soluble
substances?
A. Cholesterol
B. Phospholipid bilayer
C. Glycoproteins
D. Cytoskeleton
Answer: B – The hydrophobic interior of the phospholipid bilayer prevents free passage of polar
molecules.
15. During transcription, RNA is synthesized in which direction?
A. 3’ to 5’
B. 5’ to 3’
C. Both directions
D. Randomly
Answer: B – RNA polymerase synthesizes RNA in the 5’ → 3’ direction.
16. Which structure is only found in plant cells and not animal cells?
, A. Nucleus
B. Mitochondria
C. Chloroplast
D. Golgi apparatus
Answer: C – Chloroplasts carry out photosynthesis and are unique to plants.
17. In a dihybrid cross between two heterozygotes (AaBb × AaBb), what is the expected
phenotypic ratio?
A. 9:3:3:1
B. 3:1
C. 1:1
D. 2:1
Answer: A – The classic dihybrid cross results in 9 dominant both : 3 dominant A only : 3
dominant B only : 1 recessive both.
18. Which organelle contains hydrolytic enzymes to digest cellular waste?
A. Lysosome
B. Peroxisome
C. Ribosome
D. Endosome
Answer: A – Lysosomes break down macromolecules and damaged organelles.
19. Which phase of mitosis involves separation of sister chromatids?
A. Prophase
B. Metaphase
C. Anaphase
D. Telophase
Answer: C – Anaphase is when sister chromatids are pulled apart to opposite poles.
20. What is the complementary DNA sequence to 5’-AGTCG-3’?
A. 3’-TCAGC-5’
B. 3’-AGTCG-5’
C. 5’-TCAGC-3’
D. 3’-UCAGC-5’
Answer: A – Complementary bases pair A-T and G-C, forming 3’-TCAGC-5’.
21. Which type of bond connects amino acids in a protein?
A. Hydrogen bond
B. Ionic bond
C. Peptide bond
