Question 1

Which of the following best describes the main advantage of chromosomal microarray analysis (CMA) over traditional G-banded karyotyping in clinical genetics?

Accepted Answer

CMA provides higher resolution for detecting submicroscopic copy-number variants that are not visible by karyotyping.

Question 2

A patient presents with developmental delay and congenital anomalies. G-banded karyotyping is normal, but clinical suspicion remains high for a chromosomal disorder. Which test is most likely to reveal a pathogenic copy-number variant in this case?

Accepted Answer

Chromosomal microarray analysis (CMA)

Question 3

Which of the following statements about fluorescence in situ hybridization (FISH) is correct?

Accepted Answer

FISH uses fluorescently labeled DNA probes to detect specific DNA sequences on chromosomes.

Question 4

Which equation best represents the probability of detecting a chromosomal abnormality using G-banded karyotyping, given that the average detection rate is 1% for certain phenotypes?

Accepted Answer

$P = 0.01$

Question 5

A clinical laboratory is comparing the sensitivity of G-banded karyotyping and CMA for detecting submicroscopic deletions. Which of the following is true?

Accepted Answer

CMA is more sensitive than G-banded karyotyping for submicroscopic deletions.

Question 6

Which of the following best explains why next-generation sequencing (NGS) is increasingly used for detecting chromosomal abnormalities?

Accepted Answer

NGS provides genome-wide information at base-pair resolution, allowing detection of both copy-number variants and sequence changes.

Question 7

A newborn is suspected of having a microdeletion syndrome. Which diagnostic approach would most efficiently confirm the diagnosis?

Accepted Answer

FISH using a probe specific to the suspected microdeletion region

Question 8

Which of the following is a limitation of chromosomal microarray analysis (CMA)?

Accepted Answer

CMA cannot detect balanced chromosomal rearrangements such as translocations or inversions.

Question 9

In the context of clinical cytogenetics, what is the primary purpose of G-banding?

Accepted Answer

To produce a characteristic pattern of light and dark bands on chromosomes for identification of structural abnormalities

Question 10

A patient’s chromosomal microarray reveals a duplication of 1.5 Mb on chromosome 15. Which of the following best describes this finding?

Accepted Answer

A copy-number variant (CNV)

Question 11

Which of the following scenarios would most likely require the use of both FISH and G-banded karyotyping for diagnosis?

Accepted Answer

Identification of a complex chromosomal rearrangement involving both large and small structural changes

Question 12

Which of the following best describes the main limitation of using FISH for genome-wide screening?

Accepted Answer

FISH is limited to the detection of specific, targeted regions and is not suitable for genome-wide screening.

Question 13

A clinical geneticist is evaluating a child with unexplained intellectual disability. G-banded karyotyping is normal. What is the next best step to identify a possible chromosomal cause?

Accepted Answer

Order a chromosomal microarray analysis (CMA)

Question 14

Which of the following is true regarding the detection of mosaicism using cytogenetic techniques?

Accepted Answer

FISH can detect low-level mosaicism more sensitively than karyotyping.

Question 15

Which of the following best explains why G-banded karyotyping remains important in clinical practice despite advances in molecular techniques?

Accepted Answer

It can detect balanced chromosomal rearrangements, such as translocations and inversions, which are often missed by CMA.

Question 16

A laboratory receives a sample for prenatal diagnosis of Down syndrome. Which cytogenetic technique is most appropriate for rapid detection of trisomy 21?

Accepted Answer

FISH with a probe specific for chromosome 21

Question 17

Which of the following equations represents the calculation of copy-number variation (CNV) ratio in chromosomal microarray analysis?

Accepted Answer

$	ext{CNV ratio} = \frac{	ext{Sample intensity}}{	ext{Reference intensity}}$

Question 18

A patient’s CMA result shows a loss of genetic material on chromosome 22q11.2. Which clinical syndrome is most commonly associated with this finding?

Accepted Answer

DiGeorge syndrome

Question 19

Which of the following best describes the role of single nucleotide polymorphism (SNP) arrays in clinical cytogenetics?

Accepted Answer

SNP arrays can detect both copy-number changes and regions of homozygosity, which may indicate uniparental disomy.

Detection of Chromosomal Aberrations in Clinical Practice: From Karyotype to Genome Sequence

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