Genomic imprinting

Definition

Genomic imprinting is an epigenetic phenomenon where certain genes are expressed in a parent-of-origin-specific manner, meaning that only one allele of a gene is active while the other is silenced based on its parental origin. This selective expression can affect an organism's development and phenotype, showcasing the critical role of epigenetic mechanisms in gene regulation and inheritance patterns.

5 Must Know Facts For Your Next Test

1. Genomic imprinting occurs in mammals and is essential for normal development; abnormal imprinting can lead to various disorders.
2. Only a small number of genes are known to be imprinted, but those that are can have significant impacts on growth, metabolism, and behavior.
3. Imprinted genes are regulated through epigenetic modifications like DNA methylation and histone modifications, which establish the 'on' or 'off' state for each allele.
4. Imprinting is typically established in the germ cells during gamete formation and maintained throughout the individual's life.
5. Diseases such as Prader-Willi syndrome and Angelman syndrome are caused by errors in genomic imprinting related to the same chromosomal region but involve different parental contributions.

Review Questions

• How does genomic imprinting differ from traditional Mendelian inheritance?
  • Genomic imprinting differs from traditional Mendelian inheritance because it involves the expression of genes based on their parent of origin rather than simple dominance or recessiveness. In traditional genetics, an allele's expression is determined by its dominance over another allele. However, in genomic imprinting, one allele is silenced while the other remains active, leading to unique phenotypic outcomes depending on whether the active allele comes from the mother or father.
• Discuss the mechanisms involved in establishing and maintaining genomic imprinting in mammals.
  • The mechanisms behind genomic imprinting include DNA methylation and histone modifications, which silence one allele of an imprinted gene while allowing the other to be expressed. During gamete formation, specific methylation patterns are established that mark which allele will be active. These patterns are maintained throughout development, ensuring that the same allele remains inactive in all somatic cells. Disruption of these processes can lead to improper gene expression and associated developmental disorders.
• Evaluate the implications of genomic imprinting for understanding complex diseases and traits in humans.
  • Genomic imprinting has significant implications for understanding complex diseases and traits because it highlights how epigenetic factors can influence phenotypes beyond genetic sequences alone. By evaluating imprinted genes, researchers can better understand disorders such as obesity and neurological conditions that exhibit patterns of inheritance not explained by traditional genetics. The study of these imprinted genes also opens up avenues for potential therapeutic interventions targeting epigenetic modifications, which could lead to novel treatments for various genetic disorders.

Related terms

Epigenetics: The study of changes in gene expression that do not involve alterations to the underlying DNA sequence, often influenced by environmental factors.

Methylation: A biochemical process involving the addition of a methyl group to DNA, which can repress gene expression and play a key role in genomic imprinting.

Allele: Different forms of a gene that arise by mutation and are found at the same place on a chromosome, which can exhibit different expressions depending on imprinting.