Genomic imprinting

Definition

Genomic imprinting is an epigenetic phenomenon where certain genes are expressed in a parent-of-origin-specific manner. This means that for some genes, only the allele inherited from one parent is active, while the allele from the other parent is silenced. This selective expression plays a critical role in development and can be influenced by mechanisms such as DNA methylation and histone modifications, highlighting the complexity of gene regulation.

5 Must Know Facts For Your Next Test

1. Genomic imprinting is crucial for normal development, with disruptions often leading to disorders such as Prader-Willi syndrome and Angelman syndrome.
2. Imprinted genes are typically regulated through specific epigenetic marks established during gamete formation, making them susceptible to environmental factors.
3. Both DNA methylation and histone modifications play significant roles in maintaining the imprinted state of genes throughout cell division.
4. The expression patterns of imprinted genes can vary between different tissues and developmental stages, adding layers of complexity to their regulation.
5. In some species, genomic imprinting is essential for placental development, showcasing its evolutionary significance in mammals.

Review Questions

• How does genomic imprinting affect gene expression and what are the consequences of its disruption?
  • Genomic imprinting affects gene expression by ensuring that only one allele of certain genes is active based on parental origin. This regulation is vital for proper growth and development; if imprinted genes are disrupted, it can lead to serious developmental disorders such as Prader-Willi syndrome or Angelman syndrome. The precise control of these imprinted genes is essential for maintaining normal cellular functions and developmental processes.
• Discuss the role of DNA methylation and histone modifications in the process of genomic imprinting.
  • DNA methylation and histone modifications are key epigenetic mechanisms involved in genomic imprinting. Methylation of specific sites in the promoter regions of imprinted genes typically leads to silencing of one parental allele. Similarly, histone modifications can alter chromatin structure, making it more or less accessible for transcription. Together, these modifications help establish and maintain the imprinted state throughout an organism's development and cell divisions.
• Evaluate the implications of genomic imprinting in evolutionary biology, particularly regarding mammalian development.
  • Genomic imprinting has significant implications in evolutionary biology, especially concerning mammalian development. It may provide advantages in terms of resource allocation between parents and offspring during gestation. Imprinting can also influence traits related to growth and behavior by favoring expressions that promote successful reproductive outcomes. These selective pressures may contribute to the evolutionary persistence of imprinting as a mechanism to balance genetic contributions from both parents while adapting to environmental demands.

Related terms

DNA methylation: A biochemical process where a methyl group is added to DNA, typically acting to silence gene expression.

Histone modifications: Chemical changes to the proteins around which DNA is wrapped, influencing chromatin structure and gene accessibility.

Epigenetics:

The study of changes in gene expression that do not involve alterations to the underlying DNA sequence, often involving mechanisms like genomic imprinting.