BIOD 210 Module 5 Exam: Chromosomes &
Cytogenetics 2026/2027 – Actual Questions with
Verified Answers – Complete Practice
Examination – Portage Learning – Graded A+
Part I: Multiple Choice (30 Questions, 2 points each)
Q1: A karyotype is performed on a newborn with hypotonia, feeding difficulties, and
developmental delay. The karyotype shows two signals from chromosome 15q11-q13
on the maternally derived chromosome 15 and no signal from the paternally derived
chromosome 15. Which of the following syndromes is most likely?
A. Angelman syndrome
B. Prader-Willi syndrome [CORRECT]
C. Cri-du-chat syndrome
D. Fragile X syndrome
Correct Answer: B
Rationale: This karyotype indicates maternal uniparental disomy (UPD) or a deletion of
the paternal 15q11-q13 region. The genes in this region are imprinted, with the paternal
allele being expressed for the SNRPN gene cluster. Loss of the paternal contribution
leads to Prader-Willi syndrome (hypotonia, feeding difficulties in infancy, hyperphagia
later, developmental delay). Loss of the maternal contribution (maternal deletion or
,paternal UPD) leads to Angelman syndrome (severe intellectual disability, absent
speech, ataxia, paroxysmal laughter). Cri-du-chat involves chromosome 5p deletion.
Fragile X is a trinucleotide repeat disorder (FMR1 gene), not visible on standard
karyotype.
Q2: A patient's karyotype is reported as 47,XX,+21. Which of the following statements is
correct?
A. The patient is male with Klinefelter syndrome
B. The patient has Turner syndrome
C. The patient has Down syndrome [CORRECT]
D. The patient has a balanced translocation
Correct Answer: C
Rationale: 47,XX,+21 indicates a female (XX) with trisomy 21, which is Down syndrome.
Klinefelter syndrome is 47,XXY. Turner syndrome is 45,X. Balanced translocations show
a normal chromosome count (46) with structural rearrangements. The notation follows
ISCN standards: total chromosome number, sex chromosomes, then abnormalities (+21
indicates an extra chromosome 21).
Q3: A 25-year-old woman undergoes amniocentesis due to advanced maternal age. The
fetal karyotype is 45,X. Which clinical phenotype is expected?
A. Tall stature with normal fertility
B. Short stature, webbed neck, primary amenorrhea, and streak ovaries [CORRECT]
C. Intellectual disability with characteristic facial features
,D. Tall, sterile male with gynecomastia
Correct Answer: B
Rationale: 45,X is Turner syndrome, affecting approximately 1 in 2,500 live female
births. Characteristic features include short stature (due to SHOX gene
haploinsufficiency), webbed neck, low posterior hairline, broad chest with widely spaced
nipples, lymphedema of hands/feet at birth, primary amenorrhea due to gonadal
dysgenesis (streak ovaries), and infertility. Cardiac anomalies (coarctation of the aorta,
bicuspid aortic valve) are common. Option A describes normal female; C describes
Down syndrome; D describes Klinefelter syndrome.
Q4: Which histone modification is most commonly associated with transcriptionally
active chromatin?
A. Methylation of histone H3 at lysine 9 (H3K9me)
B. Acetylation of histone H3 at lysine 9 (H3K9ac) and lysine 27 (H3K27ac) [CORRECT]
C. Methylation of histone H3 at lysine 27 (H3K27me3)
D. Deacetylation of histone H4
Correct Answer: B
Rationale: Histone acetylation (particularly H3K9ac and H3K27ac) neutralizes positive
charges on histone tails, reducing affinity for negatively charged DNA and creating a
more open chromatin structure (euchromatin) that permits transcription. H3K9me and
H3K27me3 are repressive marks associated with heterochromatin. Histone
deacetylation generally correlates with transcriptional silencing.
, Q5: A karyotype reveals 46,XY,del(5)(p14). Which syndrome and characteristic feature
are associated with this finding?
A. Prader-Willi syndrome and hyperphagia
B. Cri-du-chat syndrome and high-pitched cry like a cat [CORRECT]
C. Angelman syndrome and ataxia
D. Williams syndrome and supravalvular aortic stenosis
Correct Answer: B
Rationale: Deletion of the short arm of chromosome 5 at band p14 results in Cri-du-chat
syndrome (5p- syndrome). The name derives from the characteristic high-pitched,
cat-like cry in infancy due to larynx abnormalities. Other features include severe
intellectual disability, microcephaly, round face in infancy (becoming long and narrow
with age), hypertelorism, and epicanthal folds. The critical region contains the CTNND2
gene. Prader-Willi (15q11-q13 deletion), Angelman (15q11-q13 maternal deletion), and
Williams (7q11.23 deletion) involve different chromosomes.
Q6: During meiosis I, homologous chromosomes fail to separate. What is this
phenomenon called, and what are its consequences?
A. Anaphase lag resulting in mosaicism
B. Nondisjunction leading to aneuploidy in gametes [CORRECT]
C. Synapsis failure leading to recombination defects
D. Chiasma interference resulting in reduced crossing over
Correct Answer: B
Cytogenetics 2026/2027 – Actual Questions with
Verified Answers – Complete Practice
Examination – Portage Learning – Graded A+
Part I: Multiple Choice (30 Questions, 2 points each)
Q1: A karyotype is performed on a newborn with hypotonia, feeding difficulties, and
developmental delay. The karyotype shows two signals from chromosome 15q11-q13
on the maternally derived chromosome 15 and no signal from the paternally derived
chromosome 15. Which of the following syndromes is most likely?
A. Angelman syndrome
B. Prader-Willi syndrome [CORRECT]
C. Cri-du-chat syndrome
D. Fragile X syndrome
Correct Answer: B
Rationale: This karyotype indicates maternal uniparental disomy (UPD) or a deletion of
the paternal 15q11-q13 region. The genes in this region are imprinted, with the paternal
allele being expressed for the SNRPN gene cluster. Loss of the paternal contribution
leads to Prader-Willi syndrome (hypotonia, feeding difficulties in infancy, hyperphagia
later, developmental delay). Loss of the maternal contribution (maternal deletion or
,paternal UPD) leads to Angelman syndrome (severe intellectual disability, absent
speech, ataxia, paroxysmal laughter). Cri-du-chat involves chromosome 5p deletion.
Fragile X is a trinucleotide repeat disorder (FMR1 gene), not visible on standard
karyotype.
Q2: A patient's karyotype is reported as 47,XX,+21. Which of the following statements is
correct?
A. The patient is male with Klinefelter syndrome
B. The patient has Turner syndrome
C. The patient has Down syndrome [CORRECT]
D. The patient has a balanced translocation
Correct Answer: C
Rationale: 47,XX,+21 indicates a female (XX) with trisomy 21, which is Down syndrome.
Klinefelter syndrome is 47,XXY. Turner syndrome is 45,X. Balanced translocations show
a normal chromosome count (46) with structural rearrangements. The notation follows
ISCN standards: total chromosome number, sex chromosomes, then abnormalities (+21
indicates an extra chromosome 21).
Q3: A 25-year-old woman undergoes amniocentesis due to advanced maternal age. The
fetal karyotype is 45,X. Which clinical phenotype is expected?
A. Tall stature with normal fertility
B. Short stature, webbed neck, primary amenorrhea, and streak ovaries [CORRECT]
C. Intellectual disability with characteristic facial features
,D. Tall, sterile male with gynecomastia
Correct Answer: B
Rationale: 45,X is Turner syndrome, affecting approximately 1 in 2,500 live female
births. Characteristic features include short stature (due to SHOX gene
haploinsufficiency), webbed neck, low posterior hairline, broad chest with widely spaced
nipples, lymphedema of hands/feet at birth, primary amenorrhea due to gonadal
dysgenesis (streak ovaries), and infertility. Cardiac anomalies (coarctation of the aorta,
bicuspid aortic valve) are common. Option A describes normal female; C describes
Down syndrome; D describes Klinefelter syndrome.
Q4: Which histone modification is most commonly associated with transcriptionally
active chromatin?
A. Methylation of histone H3 at lysine 9 (H3K9me)
B. Acetylation of histone H3 at lysine 9 (H3K9ac) and lysine 27 (H3K27ac) [CORRECT]
C. Methylation of histone H3 at lysine 27 (H3K27me3)
D. Deacetylation of histone H4
Correct Answer: B
Rationale: Histone acetylation (particularly H3K9ac and H3K27ac) neutralizes positive
charges on histone tails, reducing affinity for negatively charged DNA and creating a
more open chromatin structure (euchromatin) that permits transcription. H3K9me and
H3K27me3 are repressive marks associated with heterochromatin. Histone
deacetylation generally correlates with transcriptional silencing.
, Q5: A karyotype reveals 46,XY,del(5)(p14). Which syndrome and characteristic feature
are associated with this finding?
A. Prader-Willi syndrome and hyperphagia
B. Cri-du-chat syndrome and high-pitched cry like a cat [CORRECT]
C. Angelman syndrome and ataxia
D. Williams syndrome and supravalvular aortic stenosis
Correct Answer: B
Rationale: Deletion of the short arm of chromosome 5 at band p14 results in Cri-du-chat
syndrome (5p- syndrome). The name derives from the characteristic high-pitched,
cat-like cry in infancy due to larynx abnormalities. Other features include severe
intellectual disability, microcephaly, round face in infancy (becoming long and narrow
with age), hypertelorism, and epicanthal folds. The critical region contains the CTNND2
gene. Prader-Willi (15q11-q13 deletion), Angelman (15q11-q13 maternal deletion), and
Williams (7q11.23 deletion) involve different chromosomes.
Q6: During meiosis I, homologous chromosomes fail to separate. What is this
phenomenon called, and what are its consequences?
A. Anaphase lag resulting in mosaicism
B. Nondisjunction leading to aneuploidy in gametes [CORRECT]
C. Synapsis failure leading to recombination defects
D. Chiasma interference resulting in reduced crossing over
Correct Answer: B
