Question 1

Which of the following best describes aneuploidy?

Accepted Answer

The inheritance of either an extra chromosome (trisomy) or the loss of a chromosome (monosomy).

Question 2

A patient is diagnosed with Klinefelter's syndrome. What is the chromosomal composition of this individual?

Accepted Answer

$47,\ XXY$

Question 3

Which chromosomal abnormality is most commonly associated with Down syndrome?

Accepted Answer

Trisomy 21

Question 4

A newborn presents with severe congenital abnormalities, polydactyly, and a median survival of only 2.5 days. Karyotyping reveals $47,\ XY,\ +13$. What is the diagnosis?

Accepted Answer

Patau syndrome

Question 5

Which of the following is a structural chromosomal abnormality involving the exchange of segments between nonhomologous chromosomes?

Accepted Answer

Translocation

Question 6

A child is diagnosed with Cri du Chat syndrome. Which chromosomal event is responsible for this disorder?

Accepted Answer

Deletion of the short arm of chromosome 5

Question 7

Which prenatal diagnostic procedure is typically performed between 15 and 20 weeks of gestation to detect chromosomal abnormalities?

Accepted Answer

Amniocentesis

Question 8

Non-disjunction during meiosis can result in which of the following outcomes?

Accepted Answer

Some gametes have an extra chromosome, while others are missing one

Question 9

Which of the following is NOT a typical clinical feature of Down syndrome?

Accepted Answer

Polydactyly

Question 10

A laboratory test shows a low level of pregnancy-associated plasma protein A (PAPP-A) in the first trimester. This finding is most consistent with which fetal condition?

Accepted Answer

Down syndrome

Question 11

Which chromosomal abnormality is characterized by a female phenotype with only one X chromosome and no Barr body?

Accepted Answer

Turner syndrome

Question 12

A reciprocal translocation between chromosomes 9 and 22 results in a small chromosome 22 known as the Philadelphia chromosome. This is associated with which disease?

Accepted Answer

Chronic myelogenous leukemia

Question 13

Which of the following best describes a chromosomal inversion?

Accepted Answer

A segment of a chromosome is reversed end to end

Question 14

Which of the following is a risk factor for chromosomal non-disjunction?

Accepted Answer

Advanced maternal age

Question 15

A karyotype reveals $45,\ X$. What syndrome does this individual most likely have?

Accepted Answer

Turner syndrome

Question 16

Which of the following is a common clinical feature of Klinefelter's syndrome?

Accepted Answer

Gynecomastia

Question 17

Which chromosomal abnormality is most likely to result in spontaneous miscarriage except for trisomy 13, 18, and 21?

Accepted Answer

Monosomy of an autosome

Question 18

Which of the following best describes a duplication chromosomal abnormality?

Accepted Answer

A portion of the chromosome is present in extra copies

Question 19

Which prenatal diagnostic test is generally performed between 10 and 13 weeks of gestation and involves sampling placental tissue?

Accepted Answer

Chorionic villus sampling (CVS)

Question 20

A child presents with obesity, short stature, and mental retardation. Genetic testing reveals a deletion within $15q11.2$ inherited from the father. What is the most likely diagnosis?

Accepted Answer

Prader-Willi syndrome

Chromosomal Abnormalities: Types, Mechanisms, and Clinical Implications

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