BIOL 251 VERIFIED EXAM SOLUTIONS - COMPREHENSIVE
QUESTIONS AND ANSWERS - CURRENT VERSION (2026/2027)
1. Which organelle is responsible for synthesising ATP through oxidative
phosphorylation?
A) Nucleus
B) Mitochondria
C) Ribosome
D) Golgi apparatus
2. The fluid mosaic model describes the structure of:
A) DNA
B) The cytoskeleton
C) The plasma membrane
D) The nuclear envelope
3. Which type of endoplasmic reticulum is involved in lipid synthesis?
A) Rough ER
B) Smooth ER
C) Transitional ER
D) Nuclear ER
4. Ribosomes are composed of:
A) DNA and proteins
B) rRNA and proteins
C) mRNA and lipids
D) tRNA and enzymes
5. Which cellular structure is the site of protein sorting and modification?
A) Lysosome
B) Mitochondria
C) Golgi apparatus
D) Peroxisome
6. The nuclear envelope contains pores that allow:
, A) Only DNA to pass
B) Selective transport of macromolecules
C) Free diffusion of all molecules
D) Only lipids to cross
7. Which cytoskeletal element is responsible for cell shape and resists
compression?
A) Microfilaments
B) Intermediate filaments
C) Microtubules
D) Motor proteins
8. Lysosomes contain enzymes that function best at which pH?
A) pH 7.4
B) pH 5.0
C) pH 9.0
D) pH 6.8
9. Which process moves vesicles from the ER to the Golgi?
A) Exocytosis
B) Endocytosis
C) Anterograde transport
D) Retrograde transport
10. Peroxisomes are specialized for:
A) Protein synthesis
B) Oxidation reactions and hydrogen peroxide breakdown
C) Lipid storage
D) Calcium regulation
11. The complementary base of adenine in DNA is:
A) Guanine
B) Cytosine
C) Thymine
D) Uracil
12. During DNA replication, which enzyme synthesizes the new DNA
strand?
A) Helicase
B) DNA polymerase
, C) Ligase
D) Primase
13. Okazaki fragments are associated with synthesis on the:
A) Leading strand
B) Template strand
C) Lagging strand
D) Coding strand
14. Which enzyme unwinds the DNA double helix during replication?
A) Topoisomerase
B) Helicase
C) Primase
D) DNA polymerase III
15. In humans, each somatic cell contains how many chromosomes?
A) 23
B) 46
C) 48
D) 92
16. A gene that masks the expression of another gene is called:
A) Recessive
B) Dominant
C) Epistatic
D) Codominant
17. Which type of mutation inserts a nucleotide into the coding sequence?
A) Missense mutation
B) Nonsense mutation
C) Frameshift mutation
D) Silent mutation
18. Meiosis I is unique because it separates:
A) Sister chromatids
B) Homologous chromosomes
C) Centromeres
D) Chromatids from each other
, 19. A heterozygous individual has genotype Aa. What proportion of
offspring from Aa × Aa is expected to be homozygous dominant?
A) 1/4
B) 1/2
C) 3/4
D) 1
20. Which of the following best describes codominance?
A) One allele is completely dominant
B) Both alleles are expressed simultaneously
C) Neither allele is expressed
D) Expression depends on environment
21. During transcription, RNA polymerase reads the template strand in
which direction?
A) 5' to 3'
B) 3' to 5'
C) Both directions equally
D) From centromere outward
22. Which type of RNA carries amino acids to the ribosome?
A) mRNA
B) rRNA
C) tRNA
D) snRNA
23. The start codon in most organisms is:
A) UAA
B) UGA
C) UAG
D) AUG
24. Post-transcriptional processing in eukaryotes does NOT include:
A) 5' capping
B) Polyadenylation
C) Splicing of introns
D) Methylation of guanine bases in DNA
25. The anticodon is located on:
A) mRNA
QUESTIONS AND ANSWERS - CURRENT VERSION (2026/2027)
1. Which organelle is responsible for synthesising ATP through oxidative
phosphorylation?
A) Nucleus
B) Mitochondria
C) Ribosome
D) Golgi apparatus
2. The fluid mosaic model describes the structure of:
A) DNA
B) The cytoskeleton
C) The plasma membrane
D) The nuclear envelope
3. Which type of endoplasmic reticulum is involved in lipid synthesis?
A) Rough ER
B) Smooth ER
C) Transitional ER
D) Nuclear ER
4. Ribosomes are composed of:
A) DNA and proteins
B) rRNA and proteins
C) mRNA and lipids
D) tRNA and enzymes
5. Which cellular structure is the site of protein sorting and modification?
A) Lysosome
B) Mitochondria
C) Golgi apparatus
D) Peroxisome
6. The nuclear envelope contains pores that allow:
, A) Only DNA to pass
B) Selective transport of macromolecules
C) Free diffusion of all molecules
D) Only lipids to cross
7. Which cytoskeletal element is responsible for cell shape and resists
compression?
A) Microfilaments
B) Intermediate filaments
C) Microtubules
D) Motor proteins
8. Lysosomes contain enzymes that function best at which pH?
A) pH 7.4
B) pH 5.0
C) pH 9.0
D) pH 6.8
9. Which process moves vesicles from the ER to the Golgi?
A) Exocytosis
B) Endocytosis
C) Anterograde transport
D) Retrograde transport
10. Peroxisomes are specialized for:
A) Protein synthesis
B) Oxidation reactions and hydrogen peroxide breakdown
C) Lipid storage
D) Calcium regulation
11. The complementary base of adenine in DNA is:
A) Guanine
B) Cytosine
C) Thymine
D) Uracil
12. During DNA replication, which enzyme synthesizes the new DNA
strand?
A) Helicase
B) DNA polymerase
, C) Ligase
D) Primase
13. Okazaki fragments are associated with synthesis on the:
A) Leading strand
B) Template strand
C) Lagging strand
D) Coding strand
14. Which enzyme unwinds the DNA double helix during replication?
A) Topoisomerase
B) Helicase
C) Primase
D) DNA polymerase III
15. In humans, each somatic cell contains how many chromosomes?
A) 23
B) 46
C) 48
D) 92
16. A gene that masks the expression of another gene is called:
A) Recessive
B) Dominant
C) Epistatic
D) Codominant
17. Which type of mutation inserts a nucleotide into the coding sequence?
A) Missense mutation
B) Nonsense mutation
C) Frameshift mutation
D) Silent mutation
18. Meiosis I is unique because it separates:
A) Sister chromatids
B) Homologous chromosomes
C) Centromeres
D) Chromatids from each other
, 19. A heterozygous individual has genotype Aa. What proportion of
offspring from Aa × Aa is expected to be homozygous dominant?
A) 1/4
B) 1/2
C) 3/4
D) 1
20. Which of the following best describes codominance?
A) One allele is completely dominant
B) Both alleles are expressed simultaneously
C) Neither allele is expressed
D) Expression depends on environment
21. During transcription, RNA polymerase reads the template strand in
which direction?
A) 5' to 3'
B) 3' to 5'
C) Both directions equally
D) From centromere outward
22. Which type of RNA carries amino acids to the ribosome?
A) mRNA
B) rRNA
C) tRNA
D) snRNA
23. The start codon in most organisms is:
A) UAA
B) UGA
C) UAG
D) AUG
24. Post-transcriptional processing in eukaryotes does NOT include:
A) 5' capping
B) Polyadenylation
C) Splicing of introns
D) Methylation of guanine bases in DNA
25. The anticodon is located on:
A) mRNA
