BIOD 210 | Genetics Module 3 - Portage Learning 2026/2027 | Grade A - 100% Correct
BIOD 210 Genetics Module 3
Latest Update 2026/2027 - Portage Learning
Questions & Answers | Grade A | 100% Correct
Total Questions: 105 (multiple choice, single best answer)
Cognitive Mix: 30% Recall | 50% Application | 20% Analysis
Format: 65% application-based | 35% direct recall
Sections: 8 BIOD 210 Module 3 content domains
Time Allotted: 150 minutes (average ~86 sec per question)
Passing Standard: Portage Learning BIOD 210 - 80% correct (Grade A)
Examination Instructions
1. Each question has four response options (A, B, C, D). Select the single best answer.
2. Karyotype interpretation, mutation consequence prediction, and inheritance pattern recognition questions require
application of chromosomal and molecular genetics principles.
3. The Correct Answer and a Rationale are provided immediately beneath each question for self-study review.
4. Rationales include specific genetic mechanisms, syndrome associations, technique principles, and error analysis.
Distractors reflect common BIOD 210 student errors.
5. The bolded violet accent line marks the correct option.
SECTION 1 | Chromosome Structure and Organization Q1 - Q14
Q1. Which type of chromatin is transcriptionally active, loosely packed, and appears lightly stained under
electron microscopy?
A. Heterochromatin
B. Euchromatin - loosely packed, transcriptionally active, lightly stained [CORRECT]
C. Constitutive heterochromatin
D. Facultative heterochromatin
Correct Answer: B
Rationale: Euchromatin is the loosely packed, transcriptionally active form of chromatin that appears lightly stained.
Heterochromatin (A, C, D) is densely packed, transcriptionally inactive, and appears darkly stained. Constitutive
heterochromatin is permanently silenced (centromeres, telomeres); facultative heterochromatin can be activated
(X-inactivation).
BIOD 210 Module 3 - 105 Questions Page 1
,BIOD 210 | Genetics Module 3 - Portage Learning 2026/2027 | Grade A - 100% Correct
Q2. The fundamental repeating unit of chromatin, consisting of approximately 147 base pairs of DNA
wrapped around a histone octamer, is called a:
A. Nucleosome - 147 bp DNA wrapped around an octamer of 2 copies each of H2A, H2B, H3, and H4
[CORRECT]
B. Centromere
C. Telomere
D. Kinetochore
Correct Answer: A
Rationale: The nucleosome is the basic unit of chromatin: 147 bp of DNA wrapped 1.65 turns around a histone
octamer (2 each of H2A, H2B, H3, H4). Linker histone H1 sits between nucleosomes. The string of nucleosomes ("beads
on a string") is further compacted into 30-nm fibers, loops, and ultimately metaphase chromosomes.
Q3. Which histone protein is NOT part of the core octamer but instead binds to linker DNA between
nucleosomes?
A. H2A
B. H3
C. H1 - linker histone, sits outside the core octamer and helps compact nucleosomes into higher-order
structures [CORRECT]
D. H4
Correct Answer: C
Rationale: H1 is the linker histone that binds to the DNA between nucleosomes (linker DNA), stabilizing higher-order
chromatin structure (30-nm fiber/solenoid). The core histone octamer contains 2 copies each of H2A, H2B, H3, and H4.
H1 is not part of the octamer. Histone tails (especially H3 and H4) undergo post-translational modifications
(acetylation, methylation, phosphorylation) that regulate gene expression.
Q4. A researcher is studying centromere function. Which statement BEST describes the role of the
centromere during cell division?
A. The centromere protects chromosome ends from degradation
B. The centromere is the chromosomal region where kinetochores assemble, allowing spindle fiber
attachment for chromosome segregation during mitosis and meiosis [CORRECT]
C. The centromere contains rRNA genes
D. The centromere is where DNA replication begins
Correct Answer: B
Rationale: The centromere is the constricted region of a chromosome where the kinetochore assembles. The kinetochore
is a protein complex that attaches spindle microtubules during mitosis/meiosis, enabling chromosome segregation.
Centromeres contain alpha-satellite repeat DNA and are typically heterochromatic. Telomeres (A) protect chromosome
ends. rRNA genes are in nucleolar organizer regions. DNA replication origins are scattered throughout chromosomes.
BIOD 210 Module 3 - 105 Questions Page 2
,BIOD 210 | Genetics Module 3 - Portage Learning 2026/2027 | Grade A - 100% Correct
Q5. Human telomeres consist of thousands of tandem repeats of which DNA sequence?
A. TTAGGG repeats (5'-TTAGGG-3') - the G-rich strand, replicated by telomerase to counteract the
end-replication problem [CORRECT]
B. GGGCCC
C. AATAGGG
D. CCCTAA
Correct Answer: A
Rationale: Human telomeres consist of 5,000-15,000 bp of TTAGGG repeats (G-rich strand, with a complementary
CCCTAA strand). The G-rich strand has a 3' single-stranded overhang of 100-200 nt. Each cell division shortens
telomeres by 50-200 bp (end-replication problem). When telomeres become critically short (~4 kb), cells enter replicative
senescence (Hayflick limit). Telomerase (TERT + TERC) can extend telomeres and is active in stem cells, germline, and
~90% of cancers.
Q6. Telomerase is an enzyme that extends telomeres. In which of the following cell types is telomerase
typically ACTIVE?
A. Most adult somatic cells
B. Germline cells, stem cells, and approximately 85-90% of human cancers - telomerase is reactivated
to maintain telomere length and enable unlimited cell division [CORRECT]
C. Neurons only
D. Erythrocytes only
Correct Answer: B
Rationale: Telomerase (reverse transcriptase with an RNA template - TERC) is active in germline cells, embryonic stem
cells, and ~85-90% of cancer cells (reactivating telomerase is a hallmark of cancer, allowing unlimited proliferation).
Most adult somatic cells lack telomerase activity, leading to progressive telomere shortening and eventual replicative
senescence (Hayflick limit). The remaining 10-15% of cancers use the ALT (Alternative Lengthening of Telomeres)
pathway.
Q7. A karyotype is prepared from a patient's peripheral blood lymphocytes. Which of the following BEST
describes the procedure?
A. Cells are fixed in interphase and chromosomes are visualized as extended chromatin
B. Cells are cultured, arrested in metaphase with colchicine (which disrupts spindle fibers), fixed,
stained (typically with Giemsa for G-banding), and photographed; chromosomes are paired and
arranged by size and centromere position [CORRECT]
C. Cells are stained with fluorescent antibodies only
D. DNA is extracted and run on a gel
Correct Answer: B
Rationale: Karyotype preparation: (1) Peripheral blood lymphocytes are cultured with phytohemagglutinin (mitogen)
for 48-72 hours; (2) Colchicine is added to arrest cells in metaphase (chromosomes are maximally condensed); (3) Cells
are treated with hypotonic solution (swelling); (4) Fixed and spread on slides; (5) Stained with Giemsa (G-banding) for
banding patterns; (6) Photographed and karyotyped. Resolution: ~5-10 Mb. Higher resolution techniques: FISH (~100
kb), CMA/array CGH (~10-100 kb), sequencing (single base).
BIOD 210 Module 3 - 105 Questions Page 3
, BIOD 210 | Genetics Module 3 - Portage Learning 2026/2027 | Grade A - 100% Correct
Q8. In a standard human karyotype, how many chromosomes are present, and how are they grouped?
A. 46 chromosomes; arranged into 7 groups (A-G) based on size and centromere position, plus sex
chromosomes (XX for females, XY for males) [CORRECT]
B. 23 chromosomes, arranged by size
C. 48 chromosomes
D. 44 autosomes + 4 sex chromosomes
Correct Answer: A
Rationale: A normal human karyotype has 46 chromosomes: 22 pairs of autosomes (numbered 1-22 by size) plus 1 pair
of sex chromosomes (XX female, XY male). Chromosomes are grouped A-G: Group A (1-3, large metacentric), B (4-5,
large submetacentric), C (6-12, X, medium), D (13-15, medium acrocentric), E (16-18, short
metacentric/submetacentric), F (19-20, small metacentric), G (21-22, Y, small acrocentric). Centromere positions:
metacentric (central), submetacentric (off-center), acrocentric (near end).
Q9. The short arm of a chromosome is designated by which letter?
A. q (long arm)
B. p (short arm, from French "petit" meaning small) [CORRECT]
C. r
D. s
Correct Answer: B
Rationale: The short arm of a chromosome is designated "p" (from French "petit," meaning small). The long arm is
designated "q." Chromosomal positions are described as (chr#)(arm)(band)(sub-band), e.g., 5p15.2 = chromosome 5,
short arm, band 15, sub-band 2. This nomenclature is used in describing deletions (5p- = cri-du-chat), translocations
(t(9;22)), and other chromosomal abnormalities.
Q10. Which chromosomal structure contains the nucleolar organizer regions (NORs) in humans?
A. The long arms of the acrocentric chromosomes (13, 14, 15, 21, 22) - these contain rRNA gene
clusters that form the nucleolus [CORRECT]
B. The centromeres of all chromosomes
C. The telomeres
D. The p arms of chromosomes 1-3
Correct Answer: A
Rationale: Nucleolar organizer regions (NORs) are located on the short arms (p arms) of the five pairs of acrocentric
chromosomes (13, 14, 15, 21, 22). These regions contain clusters of ribosomal RNA (rRNA) genes (45S rRNA). The
nucleolus forms around these rRNA genes during interphase. Silver staining (Ag-NOR staining) specifically stains these
regions. Robertsonian translocations (centric fusions between acrocentric chromosomes) can involve these regions.
BIOD 210 Module 3 - 105 Questions Page 4
BIOD 210 Genetics Module 3
Latest Update 2026/2027 - Portage Learning
Questions & Answers | Grade A | 100% Correct
Total Questions: 105 (multiple choice, single best answer)
Cognitive Mix: 30% Recall | 50% Application | 20% Analysis
Format: 65% application-based | 35% direct recall
Sections: 8 BIOD 210 Module 3 content domains
Time Allotted: 150 minutes (average ~86 sec per question)
Passing Standard: Portage Learning BIOD 210 - 80% correct (Grade A)
Examination Instructions
1. Each question has four response options (A, B, C, D). Select the single best answer.
2. Karyotype interpretation, mutation consequence prediction, and inheritance pattern recognition questions require
application of chromosomal and molecular genetics principles.
3. The Correct Answer and a Rationale are provided immediately beneath each question for self-study review.
4. Rationales include specific genetic mechanisms, syndrome associations, technique principles, and error analysis.
Distractors reflect common BIOD 210 student errors.
5. The bolded violet accent line marks the correct option.
SECTION 1 | Chromosome Structure and Organization Q1 - Q14
Q1. Which type of chromatin is transcriptionally active, loosely packed, and appears lightly stained under
electron microscopy?
A. Heterochromatin
B. Euchromatin - loosely packed, transcriptionally active, lightly stained [CORRECT]
C. Constitutive heterochromatin
D. Facultative heterochromatin
Correct Answer: B
Rationale: Euchromatin is the loosely packed, transcriptionally active form of chromatin that appears lightly stained.
Heterochromatin (A, C, D) is densely packed, transcriptionally inactive, and appears darkly stained. Constitutive
heterochromatin is permanently silenced (centromeres, telomeres); facultative heterochromatin can be activated
(X-inactivation).
BIOD 210 Module 3 - 105 Questions Page 1
,BIOD 210 | Genetics Module 3 - Portage Learning 2026/2027 | Grade A - 100% Correct
Q2. The fundamental repeating unit of chromatin, consisting of approximately 147 base pairs of DNA
wrapped around a histone octamer, is called a:
A. Nucleosome - 147 bp DNA wrapped around an octamer of 2 copies each of H2A, H2B, H3, and H4
[CORRECT]
B. Centromere
C. Telomere
D. Kinetochore
Correct Answer: A
Rationale: The nucleosome is the basic unit of chromatin: 147 bp of DNA wrapped 1.65 turns around a histone
octamer (2 each of H2A, H2B, H3, H4). Linker histone H1 sits between nucleosomes. The string of nucleosomes ("beads
on a string") is further compacted into 30-nm fibers, loops, and ultimately metaphase chromosomes.
Q3. Which histone protein is NOT part of the core octamer but instead binds to linker DNA between
nucleosomes?
A. H2A
B. H3
C. H1 - linker histone, sits outside the core octamer and helps compact nucleosomes into higher-order
structures [CORRECT]
D. H4
Correct Answer: C
Rationale: H1 is the linker histone that binds to the DNA between nucleosomes (linker DNA), stabilizing higher-order
chromatin structure (30-nm fiber/solenoid). The core histone octamer contains 2 copies each of H2A, H2B, H3, and H4.
H1 is not part of the octamer. Histone tails (especially H3 and H4) undergo post-translational modifications
(acetylation, methylation, phosphorylation) that regulate gene expression.
Q4. A researcher is studying centromere function. Which statement BEST describes the role of the
centromere during cell division?
A. The centromere protects chromosome ends from degradation
B. The centromere is the chromosomal region where kinetochores assemble, allowing spindle fiber
attachment for chromosome segregation during mitosis and meiosis [CORRECT]
C. The centromere contains rRNA genes
D. The centromere is where DNA replication begins
Correct Answer: B
Rationale: The centromere is the constricted region of a chromosome where the kinetochore assembles. The kinetochore
is a protein complex that attaches spindle microtubules during mitosis/meiosis, enabling chromosome segregation.
Centromeres contain alpha-satellite repeat DNA and are typically heterochromatic. Telomeres (A) protect chromosome
ends. rRNA genes are in nucleolar organizer regions. DNA replication origins are scattered throughout chromosomes.
BIOD 210 Module 3 - 105 Questions Page 2
,BIOD 210 | Genetics Module 3 - Portage Learning 2026/2027 | Grade A - 100% Correct
Q5. Human telomeres consist of thousands of tandem repeats of which DNA sequence?
A. TTAGGG repeats (5'-TTAGGG-3') - the G-rich strand, replicated by telomerase to counteract the
end-replication problem [CORRECT]
B. GGGCCC
C. AATAGGG
D. CCCTAA
Correct Answer: A
Rationale: Human telomeres consist of 5,000-15,000 bp of TTAGGG repeats (G-rich strand, with a complementary
CCCTAA strand). The G-rich strand has a 3' single-stranded overhang of 100-200 nt. Each cell division shortens
telomeres by 50-200 bp (end-replication problem). When telomeres become critically short (~4 kb), cells enter replicative
senescence (Hayflick limit). Telomerase (TERT + TERC) can extend telomeres and is active in stem cells, germline, and
~90% of cancers.
Q6. Telomerase is an enzyme that extends telomeres. In which of the following cell types is telomerase
typically ACTIVE?
A. Most adult somatic cells
B. Germline cells, stem cells, and approximately 85-90% of human cancers - telomerase is reactivated
to maintain telomere length and enable unlimited cell division [CORRECT]
C. Neurons only
D. Erythrocytes only
Correct Answer: B
Rationale: Telomerase (reverse transcriptase with an RNA template - TERC) is active in germline cells, embryonic stem
cells, and ~85-90% of cancer cells (reactivating telomerase is a hallmark of cancer, allowing unlimited proliferation).
Most adult somatic cells lack telomerase activity, leading to progressive telomere shortening and eventual replicative
senescence (Hayflick limit). The remaining 10-15% of cancers use the ALT (Alternative Lengthening of Telomeres)
pathway.
Q7. A karyotype is prepared from a patient's peripheral blood lymphocytes. Which of the following BEST
describes the procedure?
A. Cells are fixed in interphase and chromosomes are visualized as extended chromatin
B. Cells are cultured, arrested in metaphase with colchicine (which disrupts spindle fibers), fixed,
stained (typically with Giemsa for G-banding), and photographed; chromosomes are paired and
arranged by size and centromere position [CORRECT]
C. Cells are stained with fluorescent antibodies only
D. DNA is extracted and run on a gel
Correct Answer: B
Rationale: Karyotype preparation: (1) Peripheral blood lymphocytes are cultured with phytohemagglutinin (mitogen)
for 48-72 hours; (2) Colchicine is added to arrest cells in metaphase (chromosomes are maximally condensed); (3) Cells
are treated with hypotonic solution (swelling); (4) Fixed and spread on slides; (5) Stained with Giemsa (G-banding) for
banding patterns; (6) Photographed and karyotyped. Resolution: ~5-10 Mb. Higher resolution techniques: FISH (~100
kb), CMA/array CGH (~10-100 kb), sequencing (single base).
BIOD 210 Module 3 - 105 Questions Page 3
, BIOD 210 | Genetics Module 3 - Portage Learning 2026/2027 | Grade A - 100% Correct
Q8. In a standard human karyotype, how many chromosomes are present, and how are they grouped?
A. 46 chromosomes; arranged into 7 groups (A-G) based on size and centromere position, plus sex
chromosomes (XX for females, XY for males) [CORRECT]
B. 23 chromosomes, arranged by size
C. 48 chromosomes
D. 44 autosomes + 4 sex chromosomes
Correct Answer: A
Rationale: A normal human karyotype has 46 chromosomes: 22 pairs of autosomes (numbered 1-22 by size) plus 1 pair
of sex chromosomes (XX female, XY male). Chromosomes are grouped A-G: Group A (1-3, large metacentric), B (4-5,
large submetacentric), C (6-12, X, medium), D (13-15, medium acrocentric), E (16-18, short
metacentric/submetacentric), F (19-20, small metacentric), G (21-22, Y, small acrocentric). Centromere positions:
metacentric (central), submetacentric (off-center), acrocentric (near end).
Q9. The short arm of a chromosome is designated by which letter?
A. q (long arm)
B. p (short arm, from French "petit" meaning small) [CORRECT]
C. r
D. s
Correct Answer: B
Rationale: The short arm of a chromosome is designated "p" (from French "petit," meaning small). The long arm is
designated "q." Chromosomal positions are described as (chr#)(arm)(band)(sub-band), e.g., 5p15.2 = chromosome 5,
short arm, band 15, sub-band 2. This nomenclature is used in describing deletions (5p- = cri-du-chat), translocations
(t(9;22)), and other chromosomal abnormalities.
Q10. Which chromosomal structure contains the nucleolar organizer regions (NORs) in humans?
A. The long arms of the acrocentric chromosomes (13, 14, 15, 21, 22) - these contain rRNA gene
clusters that form the nucleolus [CORRECT]
B. The centromeres of all chromosomes
C. The telomeres
D. The p arms of chromosomes 1-3
Correct Answer: A
Rationale: Nucleolar organizer regions (NORs) are located on the short arms (p arms) of the five pairs of acrocentric
chromosomes (13, 14, 15, 21, 22). These regions contain clusters of ribosomal RNA (rRNA) genes (45S rRNA). The
nucleolus forms around these rRNA genes during interphase. Silver staining (Ag-NOR staining) specifically stains these
regions. Robertsonian translocations (centric fusions between acrocentric chromosomes) can involve these regions.
BIOD 210 Module 3 - 105 Questions Page 4
