BIOD 210 MODULE 5 EXAM 2026/2027 |
Chromosome Structure, Cell Division & Gene
Mapping | Latest Q&A Verified | Portage Learning
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Q1: Which histone protein forms the core octamer around which DNA wraps to form a
nucleosome?
A. H1 only
B. H2A, H2B, H3, and H4 [CORRECT]
C. H1, H2A, H2B, and H3
D. H3 and H4 only
Correct Answer: B
Rationale: The nucleosome core particle consists of an octamer containing two copies
each of histones H2A, H2B, H3, and H4. Approximately 147 base pairs of DNA wrap
around this octamer 1.65 times. H1 is a linker histone that binds to the DNA entering
and exiting the nucleosome but is not part of the core octamer. Option A is incorrect
because H1 alone cannot form the octamer. Option C incorrectly includes H1 in the core
structure. Option D is incomplete as it omits H2A and H2B, which are essential
components of the octamer.
Q2: During which phase of interphase does DNA replication occur?
A. G1 phase
B. S phase [CORRECT]
C. G2 phase
D. M phase
Correct Answer: B
Rationale: The S (synthesis) phase is when DNA replication occurs, resulting in the
duplication of chromosomes. During G1 phase (Option A), the cell grows and prepares
,for DNA synthesis but does not replicate DNA. G2 phase (Option C) involves continued
growth and preparation for mitosis, but DNA replication is already complete. M phase
(Option D) is mitosis itself, where replicated chromosomes are segregated, not
synthesized.
Q3: In euchromatin compared to heterochromatin:
A. DNA is more tightly packed and transcriptionally active
B. DNA is less condensed and transcriptionally active [CORRECT]
C. DNA is found only at the nuclear periphery
D. Histone acetylation is absent
Correct Answer: B
Rationale: Euchromatin represents loosely packed chromatin that is accessible to
transcription machinery and therefore transcriptionally active. Heterochromatin (Option
A reversed) is tightly packed and transcriptionally inactive. Option C describes
heterochromatin localization, not euchromatin. Option D is incorrect because histone
acetylation is actually enriched in euchromatin, where it loosens chromatin structure to
promote transcription; heterochromatin is characterized by histone deacetylation and
methylation.
Q4: Which checkpoint ensures that DNA replication is complete before the cell enters
mitosis?
A. G1/S checkpoint
B. Intra-S checkpoint
C. G2/M checkpoint [CORRECT]
D. Spindle assembly checkpoint
Correct Answer: C
Rationale: The G2/M checkpoint verifies that DNA replication is complete and checks
for DNA damage before the cell commits to mitosis. The G1/S checkpoint (Option A)
monitors cell size, nutrient availability, and DNA damage before replication begins. The
intra-S checkpoint (Option B) monitors DNA replication progress and responds to
, replication stress during S phase. The spindle assembly checkpoint (Option D) operates
during metaphase to ensure proper chromosome attachment to spindle fibers.
Q5: During prophase of mitosis, which event occurs?
A. Chromosomes align at the metaphase plate
B. Sister chromatids separate and move to opposite poles
C. Chromatin condenses into visible chromosomes and the nuclear envelope breaks
down [CORRECT]
D. Cytokinesis begins
Correct Answer: C
Rationale: Prophase is characterized by chromatin condensation into visible
chromosomes, disappearance of the nucleolus, and breakdown of the nuclear envelope.
Option A describes metaphase. Option B describes anaphase. Option D describes
telophase/cytokinesis. These temporal distinctions are crucial for understanding cell
cycle progression.
Q6: The recombination frequency between two genes is 12%. What is the approximate
map distance between these genes?
A. 6 map units
B. 12 map units [CORRECT]
C. 24 map units
D. Cannot be determined from this information
Correct Answer: B
Rationale: One percent recombination frequency equals one map unit (centiMorgan,
cM). Therefore, 12% recombination frequency equals 12 map units. This 1:1 relationship
holds for distances less than 10-15 map units; however, for this calculation, 12 map
units is the direct conversion. Option A incorrectly halves the value. Option C incorrectly
doubles it. Option D is incorrect because recombination frequency directly estimates
map distance for closely linked genes.
Q7: In a three-point test cross, the parental (non-recombinant) phenotypes appear most
frequently because:
Chromosome Structure, Cell Division & Gene
Mapping | Latest Q&A Verified | Portage Learning
| Pass Guaranteed - A+ Graded
Q1: Which histone protein forms the core octamer around which DNA wraps to form a
nucleosome?
A. H1 only
B. H2A, H2B, H3, and H4 [CORRECT]
C. H1, H2A, H2B, and H3
D. H3 and H4 only
Correct Answer: B
Rationale: The nucleosome core particle consists of an octamer containing two copies
each of histones H2A, H2B, H3, and H4. Approximately 147 base pairs of DNA wrap
around this octamer 1.65 times. H1 is a linker histone that binds to the DNA entering
and exiting the nucleosome but is not part of the core octamer. Option A is incorrect
because H1 alone cannot form the octamer. Option C incorrectly includes H1 in the core
structure. Option D is incomplete as it omits H2A and H2B, which are essential
components of the octamer.
Q2: During which phase of interphase does DNA replication occur?
A. G1 phase
B. S phase [CORRECT]
C. G2 phase
D. M phase
Correct Answer: B
Rationale: The S (synthesis) phase is when DNA replication occurs, resulting in the
duplication of chromosomes. During G1 phase (Option A), the cell grows and prepares
,for DNA synthesis but does not replicate DNA. G2 phase (Option C) involves continued
growth and preparation for mitosis, but DNA replication is already complete. M phase
(Option D) is mitosis itself, where replicated chromosomes are segregated, not
synthesized.
Q3: In euchromatin compared to heterochromatin:
A. DNA is more tightly packed and transcriptionally active
B. DNA is less condensed and transcriptionally active [CORRECT]
C. DNA is found only at the nuclear periphery
D. Histone acetylation is absent
Correct Answer: B
Rationale: Euchromatin represents loosely packed chromatin that is accessible to
transcription machinery and therefore transcriptionally active. Heterochromatin (Option
A reversed) is tightly packed and transcriptionally inactive. Option C describes
heterochromatin localization, not euchromatin. Option D is incorrect because histone
acetylation is actually enriched in euchromatin, where it loosens chromatin structure to
promote transcription; heterochromatin is characterized by histone deacetylation and
methylation.
Q4: Which checkpoint ensures that DNA replication is complete before the cell enters
mitosis?
A. G1/S checkpoint
B. Intra-S checkpoint
C. G2/M checkpoint [CORRECT]
D. Spindle assembly checkpoint
Correct Answer: C
Rationale: The G2/M checkpoint verifies that DNA replication is complete and checks
for DNA damage before the cell commits to mitosis. The G1/S checkpoint (Option A)
monitors cell size, nutrient availability, and DNA damage before replication begins. The
intra-S checkpoint (Option B) monitors DNA replication progress and responds to
, replication stress during S phase. The spindle assembly checkpoint (Option D) operates
during metaphase to ensure proper chromosome attachment to spindle fibers.
Q5: During prophase of mitosis, which event occurs?
A. Chromosomes align at the metaphase plate
B. Sister chromatids separate and move to opposite poles
C. Chromatin condenses into visible chromosomes and the nuclear envelope breaks
down [CORRECT]
D. Cytokinesis begins
Correct Answer: C
Rationale: Prophase is characterized by chromatin condensation into visible
chromosomes, disappearance of the nucleolus, and breakdown of the nuclear envelope.
Option A describes metaphase. Option B describes anaphase. Option D describes
telophase/cytokinesis. These temporal distinctions are crucial for understanding cell
cycle progression.
Q6: The recombination frequency between two genes is 12%. What is the approximate
map distance between these genes?
A. 6 map units
B. 12 map units [CORRECT]
C. 24 map units
D. Cannot be determined from this information
Correct Answer: B
Rationale: One percent recombination frequency equals one map unit (centiMorgan,
cM). Therefore, 12% recombination frequency equals 12 map units. This 1:1 relationship
holds for distances less than 10-15 map units; however, for this calculation, 12 map
units is the direct conversion. Option A incorrectly halves the value. Option C incorrectly
doubles it. Option D is incorrect because recombination frequency directly estimates
map distance for closely linked genes.
Q7: In a three-point test cross, the parental (non-recombinant) phenotypes appear most
frequently because:
