Question 1

Which chromosomal abnormality is most commonly associated with an extra copy of chromosome 21, and what is the medical term for this condition?

Accepted Answer

Down syndrome; trisomy 21

Question 2

A female patient presents with short stature, webbed neck, and is sterile, but has normal intelligence. Which chromosomal abnormality is most likely present?

Accepted Answer

XO (Turner syndrome)

Question 3

Which of the following best describes the mechanism by which Down syndrome can occur due to a structural change in chromosomes?

Accepted Answer

Translocation of a piece of chromosome 21 to chromosome 14

Question 4

What is the most likely outcome of nondisjunction during meiosis I, as shown in the diagram, in terms of chromosome number in gametes?

Accepted Answer

Half of gametes have $$n+1$$ and half have $$n-1$$ chromosomes

Question 5

A male patient is tall, has acne, and an increased risk of learning problems. His karyotype shows an extra Y chromosome. What syndrome does he most likely have?

Accepted Answer

Supermale syndrome (XYY)

Question 6

Which chromosomal abnormality is associated with duplication of part of chromosome 17 and results in Charcot-Marie-Tooth disease?

Accepted Answer

Duplication

Question 7

What is the risk of miscarriage associated with chorionic villus sampling (CVS) compared to amniocentesis?

Accepted Answer

CVS has a higher risk than amniocentesis

Question 8

Which syndrome is caused by the expansion or lengthening of the FMR1 gene on the X chromosome, resulting in intellectual disability?

Accepted Answer

Fragile X syndrome

Question 9

A karyotype shows a female with four X chromosomes. Which syndrome does this represent, and what is a common symptom?

Accepted Answer

Tetrasomy X; intellectual disability

Question 10

Which chromosomal abnormality is most likely to result in a phenotype with short stature, craniofacial abnormalities, and intellectual disability due to five X chromosomes?

Accepted Answer

XXXXX syndrome (Pentasomy X)

Question 11

Which chromosomal abnormality is associated with a deletion of part of chromosome 4 and results in Wolf-Hirschhorn syndrome?

Accepted Answer

Deletion

Question 12

What is the relationship between maternal age and the incidence of Down syndrome, as shown in the graph?

Accepted Answer

Incidence increases sharply after age 35

Question 13

Which chromosomal abnormality is characterized by a male with XXY chromosomes, tall stature, breast enlargement, and sterility?

Accepted Answer

Klinefelter syndrome

Question 14

Which prenatal testing method involves extracting amniotic fluid from the uterus and carries a risk of miscarriage between 0.25%-0.50%?

Accepted Answer

Amniocentesis

Question 15

Which chromosomal abnormality is most likely to result in a female with three X chromosomes, and what is a common symptom?

Accepted Answer

XXX syndrome; language difficulties

Question 16

Which event during meiosis is most likely to result in gametes with abnormal chromosome numbers, leading to disorders such as trisomy or monosomy?

Accepted Answer

Nondisjunction

Question 17

A patient has a karyotype showing a piece of chromosome 21 attached to chromosome 14. What is the name of this chromosomal structural abnormality?

Accepted Answer

Translocation

Question 18

Which syndrome is the second most common genetic cause of mental disabilities after Down syndrome and is caused by a mutation in the FMR1 gene?

Accepted Answer

Fragile X syndrome

Question 19

Which chromosomal abnormality is most likely to result in a male with mild-moderate developmental delay, large irregular teeth, tall stature, and acne due to three Y chromosomes?

Accepted Answer

XYYY syndrome

Question 20

Which chromosomal structural change involves a segment of a chromosome being reversed end to end?

Accepted Answer

Inversion

Chromosomal Abnormalities: Number and Structure Changes in Humans

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