Genomic imprinting

Definition

Genomic imprinting is an epigenetic phenomenon where genes are expressed in a parent-of-origin-specific manner, meaning that only one allele of a gene is expressed while the other is silenced based on whether it was inherited from the mother or the father. This unique gene expression is crucial for normal development and is regulated by DNA methylation and other epigenetic marks, which can influence various biological processes and contribute to certain diseases.

5 Must Know Facts For Your Next Test

1. Genomic imprinting affects a relatively small number of genes but has a profound impact on growth and development.
2. Imprinted genes are regulated by specific epigenetic modifications, including DNA methylation and histone modifications, that determine whether they are active or silenced.
3. Imprinting disorders, such as Prader-Willi syndrome and Angelman syndrome, occur due to the loss of expression of specific imprinted genes, leading to distinct phenotypic outcomes.
4. The establishment of genomic imprinting occurs during gametogenesis, where methylation patterns are reset in both sperm and egg cells before fertilization.
5. Environmental factors, such as nutrition and stress, can influence epigenetic marks and potentially alter genomic imprinting patterns across generations.

Review Questions

• How does genomic imprinting influence gene expression and what role do epigenetic marks play in this process?
  • Genomic imprinting influences gene expression by ensuring that only one allele of an imprinted gene is expressed, depending on whether it is inherited from the mother or father. This selective expression is maintained through epigenetic marks such as DNA methylation and histone modifications, which control the accessibility of the gene for transcription. These modifications can lead to either activation or silencing of the imprinted allele, playing a critical role in normal development and cellular functions.
• Discuss the implications of genomic imprinting in the context of developmental disorders and provide examples.
  • Genomic imprinting has significant implications for developmental disorders because improper regulation of imprinted genes can lead to various health issues. For example, Prader-Willi syndrome results from the lack of expression of paternal genes on chromosome 15, while Angelman syndrome arises from the loss of maternal gene expression on the same chromosome. Both conditions highlight how critical proper imprinting is for normal growth and neurological function, showcasing the importance of understanding these mechanisms in clinical settings.
• Evaluate how environmental factors can alter genomic imprinting and discuss potential long-term effects on health across generations.
  • Environmental factors such as diet, stress, and exposure to toxins can influence epigenetic modifications that regulate genomic imprinting. For example, maternal nutrition during pregnancy may affect the methylation patterns of genes in offspring, potentially leading to long-term health effects like obesity or metabolic disorders. These changes can be passed down through generations, indicating that lifestyle and environmental influences play a crucial role in shaping the epigenome and may have lasting impacts on future generations' health outcomes.

Related terms

DNA methylation: A biochemical process where a methyl group is added to the DNA molecule, typically at cytosine bases, which can silence gene expression.

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

allele:

Different versions of a gene that may produce distinguishable phenotypic effects, which can be inherited from one or both parents.