ABMGG Cytogenetics and Chromosomal Analysis 2

Question 1

The Philadelphia chromosome, found in chronic myelogenous leukemia (CML), results from which chromosomal rearrangement?

Accepted Answer

Reciprocal translocation t(9;22)(q34;q11.2)

Answer

The Philadelphia chromosome is formed by t(9;22)(q34;q11.2), which fuses BCR on chromosome 22 with ABL1 on chromosome 9 to create the oncogenic BCR::ABL1 fusion gene.

Question 2

A pericentric inversion involves a chromosomal segment that:

Accepted Answer

Spans the centromere, including both arms

Answer

A pericentric inversion includes the centromere, with breakpoints in both the short (p) and long (q) arms, potentially changing the chromosome's arm ratio.

Question 3

A carrier of a balanced reciprocal translocation is at risk of producing offspring with which abnormality?

Accepted Answer

Offspring with unbalanced chromosomal segments causing partial monosomy or trisomy

Answer

During meiosis, a balanced translocation carrier can produce unbalanced gametes through 3:1 or 2:2 segregation, resulting in offspring with partial monosomy or partial trisomy.

Question 4

Chromosomal mosaicism in a patient is BEST defined as:

Accepted Answer

The presence of two or more cytogenetically distinct cell lines from the same zygote

Answer

Mosaicism is the coexistence of two or more cell populations with different chromosomal constitutions arising from a single zygote, typically due to a post-zygotic mitotic error.

Question 5

Uniparental disomy (UPD) can cause disease even when both copies of a chromosome are structurally normal primarily because of:

Accepted Answer

Genomic imprinting causing silencing of maternally or paternally imprinted genes

Answer

Genomic imprinting silences certain genes depending on parental origin; UPD can result in either two silenced (imprinted) copies or two expressed copies, disrupting normal gene dosage for imprinted loci.

ABMGG - American Board of Medical Genetics and Genomics Practice Test

ABMGG - American Board of Medical Genetics and Genomics Practice Test

ABMGG Cytogenetics and Chromosomal Analysis 2