BIOL 101 Exam 3 V1 | BIOL 101 Principles of Biology | Actual Q&A
with Rationale (BIOL101 Exam 3) | Liberty University
1. During which phase of meiosis do homologous chromosomes separate from one another?
A. Prophase I
B. Metaphase I
C. Anaphase II
D. Anaphase I
Correct Answer: D
Explanation: In Anaphase I, the spindle fibers pull the homologous pairs apart toward
opposite poles. This process is essential for reducing the chromosome number from diploid
to haploid. Sister chromatids remain attached at the centromere until the second division
stage.
2. If a plant with red flowers (RR) is crossed with a plant with white flowers (rr) and all
offspring have pink flowers, what inheritance pattern is displayed?
A. Incomplete dominance
B. Codominance
C. Complete dominance
D. Polygenic inheritance
Correct Answer: A
Explanation: Incomplete dominance occurs when the phenotype of the heterozygote is an
intermediate blend of the two homozygous phenotypes. In this case, neither the red nor the
white allele is fully dominant over the other. This results in the production of a third
phenotype, which is pink.
3. Which enzyme is responsible for unwinding the DNA double helix during the process of
replication?
A. DNA Polymerase III
B. RNA Primase
C. Ligase
D. Helicase
Correct Answer: D
,Explanation: Helicase acts by breaking the hydrogen bonds between the nitrogenous
bases of the two DNA strands. This creates the replication fork which allows other enzymes
to access the single strands. Without helicase activity, the replication process cannot
initiate or proceed.
4. In a DNA molecule, if 30% of the bases are Cytosine, what percentage of the bases are
Thymine?
A. 20%
B. 70%
C. 30%
D. 40%
Correct Answer: A
Explanation: According to Chargaff’s rules, the amount of Cytosine equals Guanine, so G is
also 30%, totaling 60% for C-G pairs. This leaves 40% for Adenine and Thymine combined.
Since Adenine equals Thymine, each must represent 20% of the total DNA bases.
5. Which of the following describes the ‘Central Dogma’ of molecular biology?
A. RNA -> DNA -> Protein
B. Protein -> RNA -> DNA
C. DNA -> RNA -> Protein
D. DNA -> Protein -> RNA
Correct Answer: C
Explanation: The Central Dogma describes the standard two-step process of gene
expression in biological systems. Information is first transcribed from a DNA template into
messenger RNA. This mRNA is then translated by ribosomes into a functional polypeptide
chain.
6. What is the primary function of tRNA during the process of translation?
A. To synthesize mRNA in the nucleus
B. To serve as the template for protein synthesis
C. To catalyze the formation of peptide bonds
D. To carry specific amino acids to the ribosome
Correct Answer: D
Explanation: Transfer RNA molecules possess an anticodon that matches a specific codon
on the mRNA strand. They transport the corresponding amino acids to the ribosome to
, build the protein chain. This ensures that the genetic code is accurately converted into a
sequence of amino acids.
7. A human cell containing 22 autosomes and a Y chromosome is likely to be:
A. A somatic cell of a male
B. A sperm cell
C. A somatic cell of a female
D. An unfertilized egg cell
Correct Answer: B
Explanation: Sperm cells are haploid gametes produced by males containing 23
chromosomes in total. The presence of a Y chromosome indicates the gamete originated
from a male and will determine the male sex of the zygote. Autosomes number 22 in a
haploid human cell, accompanied by one sex chromosome.
8. Which scientist(s) are credited with determining the double-helical structure of DNA?
A. Gregor Mendel
B. Charles Darwin
C. Hershey and Chase
D. Watson and Crick
Correct Answer: D
Explanation: James Watson and Francis Crick published the double helix model in 1953
based on X-ray diffraction data. Their model correctly proposed the antiparallel nature of
the sugar-phosphate backbones. This discovery revolutionized the field of genetics and
molecular biology.
9. What occurs during the process of crossing over in meiosis?
A. Replication of DNA molecules
B. Separation of sister chromatids
C. Independent assortment of chromosomes
D. Exchange of genetic material between non-sister chromatids
Correct Answer: D
Explanation: Crossing over occurs during Prophase I when homologous chromosomes
pair up to form tetrads. This physical exchange of DNA segments creates new combinations
of alleles on a single chromosome. It is a major source of genetic variation in sexually
reproducing organisms.
with Rationale (BIOL101 Exam 3) | Liberty University
1. During which phase of meiosis do homologous chromosomes separate from one another?
A. Prophase I
B. Metaphase I
C. Anaphase II
D. Anaphase I
Correct Answer: D
Explanation: In Anaphase I, the spindle fibers pull the homologous pairs apart toward
opposite poles. This process is essential for reducing the chromosome number from diploid
to haploid. Sister chromatids remain attached at the centromere until the second division
stage.
2. If a plant with red flowers (RR) is crossed with a plant with white flowers (rr) and all
offspring have pink flowers, what inheritance pattern is displayed?
A. Incomplete dominance
B. Codominance
C. Complete dominance
D. Polygenic inheritance
Correct Answer: A
Explanation: Incomplete dominance occurs when the phenotype of the heterozygote is an
intermediate blend of the two homozygous phenotypes. In this case, neither the red nor the
white allele is fully dominant over the other. This results in the production of a third
phenotype, which is pink.
3. Which enzyme is responsible for unwinding the DNA double helix during the process of
replication?
A. DNA Polymerase III
B. RNA Primase
C. Ligase
D. Helicase
Correct Answer: D
,Explanation: Helicase acts by breaking the hydrogen bonds between the nitrogenous
bases of the two DNA strands. This creates the replication fork which allows other enzymes
to access the single strands. Without helicase activity, the replication process cannot
initiate or proceed.
4. In a DNA molecule, if 30% of the bases are Cytosine, what percentage of the bases are
Thymine?
A. 20%
B. 70%
C. 30%
D. 40%
Correct Answer: A
Explanation: According to Chargaff’s rules, the amount of Cytosine equals Guanine, so G is
also 30%, totaling 60% for C-G pairs. This leaves 40% for Adenine and Thymine combined.
Since Adenine equals Thymine, each must represent 20% of the total DNA bases.
5. Which of the following describes the ‘Central Dogma’ of molecular biology?
A. RNA -> DNA -> Protein
B. Protein -> RNA -> DNA
C. DNA -> RNA -> Protein
D. DNA -> Protein -> RNA
Correct Answer: C
Explanation: The Central Dogma describes the standard two-step process of gene
expression in biological systems. Information is first transcribed from a DNA template into
messenger RNA. This mRNA is then translated by ribosomes into a functional polypeptide
chain.
6. What is the primary function of tRNA during the process of translation?
A. To synthesize mRNA in the nucleus
B. To serve as the template for protein synthesis
C. To catalyze the formation of peptide bonds
D. To carry specific amino acids to the ribosome
Correct Answer: D
Explanation: Transfer RNA molecules possess an anticodon that matches a specific codon
on the mRNA strand. They transport the corresponding amino acids to the ribosome to
, build the protein chain. This ensures that the genetic code is accurately converted into a
sequence of amino acids.
7. A human cell containing 22 autosomes and a Y chromosome is likely to be:
A. A somatic cell of a male
B. A sperm cell
C. A somatic cell of a female
D. An unfertilized egg cell
Correct Answer: B
Explanation: Sperm cells are haploid gametes produced by males containing 23
chromosomes in total. The presence of a Y chromosome indicates the gamete originated
from a male and will determine the male sex of the zygote. Autosomes number 22 in a
haploid human cell, accompanied by one sex chromosome.
8. Which scientist(s) are credited with determining the double-helical structure of DNA?
A. Gregor Mendel
B. Charles Darwin
C. Hershey and Chase
D. Watson and Crick
Correct Answer: D
Explanation: James Watson and Francis Crick published the double helix model in 1953
based on X-ray diffraction data. Their model correctly proposed the antiparallel nature of
the sugar-phosphate backbones. This discovery revolutionized the field of genetics and
molecular biology.
9. What occurs during the process of crossing over in meiosis?
A. Replication of DNA molecules
B. Separation of sister chromatids
C. Independent assortment of chromosomes
D. Exchange of genetic material between non-sister chromatids
Correct Answer: D
Explanation: Crossing over occurs during Prophase I when homologous chromosomes
pair up to form tetrads. This physical exchange of DNA segments creates new combinations
of alleles on a single chromosome. It is a major source of genetic variation in sexually
reproducing organisms.
