ABMGG ABMGG Molecular Genetics and Genomics Techniques 2

Question 1

What does fluorescence in situ hybridization (FISH) detect that a standard G-banded karyotype typically cannot?

Accepted Answer

Submicroscopic deletions at specific loci

Answer

FISH uses labeled probes to detect deletions or duplications at targeted loci below the ~5–10 Mb resolution of conventional karyotyping.

Question 2

Which sequencing methodology is used to detect epigenetic modifications such as DNA methylation patterns relevant to imprinting disorders?

Accepted Answer

Bisulfite sequencing

Answer

Bisulfite treatment converts unmethylated cytosines to uracil while leaving methylated cytosines intact, enabling methylation mapping by sequencing.

Question 3

RNA sequencing (RNA-seq) adds clinical value in medical genetics primarily by:

Accepted Answer

Identifying splicing defects and allele-specific expression abnormalities

Answer

RNA-seq can reveal aberrant splicing caused by deep intronic variants and confirm whether a variant affects gene expression, increasing diagnostic yield.

Question 4

In the context of ABMGG laboratory practice, what is a mosaic variant?

Accepted Answer

A variant present in only a subset of an individual's cells

Answer

Mosaicism arises when a post-zygotic mutation occurs in a progenitor cell, resulting in two or more genetically distinct cell populations within the same individual.

Question 5

Which term describes a variant that arose newly in a patient and is not present in either biological parent?

Accepted Answer

De novo variant

Answer

A de novo variant occurs as a new mutation in the proband and is confirmed by demonstrating its absence in both parents via trio sequencing or targeted testing.

ABMGG - American Board of Medical Genetics and Genomics Practice Test

ABMGG - American Board of Medical Genetics and Genomics Practice Test

ABMGG ABMGG Molecular Genetics and Genomics Techniques 2