Genomics & Molecular Biology Flashcards

Epigenetics refers to changes in gene expression that are:

Answer: Heritable changes in gene activity not involving changes to the underlying DNA sequence

Epigenetic modifications, including DNA methylation and histone modification, regulate gene expression heritably without altering the DNA sequence itself.

In the clinical genomics laboratory, variant interpretation follows which internationally recognised classification system?

Answer: The ACMG/AMP five-tier variant classification (Pathogenic to Benign)

The American College of Medical Genetics and Genomics (ACMG)/AMP 2015 guidelines provide a five-tier system (Pathogenic, Likely Pathogenic, VUS, Likely Benign, Benign) widely used in clinical genomics reporting.

What is a microsatellite in the context of genomic analysis?

Answer: A short tandemly repeated sequence (1–6 bp repeat unit) distributed throughout the genome

Microsatellites (STRs) are tandem repeats of 1–6 bp units that vary in repeat number between individuals, making them informative markers for identity testing, linkage analysis, and MSI assessment.

Bioinformatics pipelines in clinical genomics typically include which sequence of steps?

Answer: Base calling → alignment to reference genome → variant calling → annotation and filtering

Standard NGS bioinformatics pipelines convert raw signal to base calls, align reads to a reference genome, identify variants, then annotate and filter against databases and quality thresholds before clinical interpretation.

Loss of heterozygosity (LOH) in tumour genomics indicates:

Answer: Loss of one allele at a locus, often revealing a recessive mutation in the remaining allele

LOH occurs when one allele at a heterozygous locus is deleted or otherwise lost in somatic cells; if the retained allele carries a pathogenic variant, it becomes unmasked, consistent with Knudson's two-hit hypothesis.

The term 'allele frequency' in a population genetics context describes:

Answer: The proportion of all alleles at a given locus in the population that are of a specific variant type

Allele frequency is the relative proportion of a specific allele among all alleles at that locus across all individuals in a population, a fundamental parameter in population genetics and variant interpretation.

Comparative genomic hybridisation (CGH) array analysis is used primarily to detect:

Answer: Genome-wide copy number gains and losses at sub-megabase resolution

Array CGH compares patient and reference DNA hybridised to probes across the genome, revealing copy number gains and losses that are below the resolution of conventional cytogenetics.