# DBT JRF 2022 — Question 51

Exam: DBT JRF 2022 · Section: B · Topic: Genetics › Genomic Imprinting & Epigenetics · Difficulty: Medium

## Question

Differential expression of the genetic material depending on its parentage of inheritance is known as:

## Options

- **A.** Penetrance
- **B.** Expressivity
- **C.** Epistasis
- **D.** Genomic Imprinting

## Answer

Option D

## Explanation

Genomic imprinting: Genomic imprinting is an epigenetic mechanism by which certain genes are expressed in a PARENT-OF-ORIGIN-SPECIFIC manner: • The same allele (same DNA sequence) is expressed OR silenced depending on whether it was inherited from the MOTHER or the FATHER. • Imprinting is established in the germline and maintained through DNA methylation and histone modifications. Classic examples: • IGF2 (Insulin-like Growth Factor 2): Only the PATERNAL allele is expressed; maternal allele is silenced. • H19 (long non-coding RNA): Only the MATERNAL allele is expressed; paternal allele is silenced. • SNRPN, KCNQ1: Imprinted genes on chromosome 15 and 11; disruption causes Prader-Willi and Angelman syndromes, respectively. This differs from standard Mendelian inheritance where both alleles are expressed equally. Answer: Genomic imprinting = epigenetic differential gene expression based on parental origin.

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