DNA methylation

Definition

DNA methylation is a biochemical process involving the addition of a methyl group to the DNA molecule, typically at the cytosine base in a CpG dinucleotide context. This process plays a crucial role in regulating gene expression and is a key mechanism in epigenetics, influencing how genes are turned on or off without altering the underlying DNA sequence.

5 Must Know Facts For Your Next Test

1. DNA methylation typically occurs at cytosine residues that are followed by guanine (CpG sites), where a methyl group is added to the carbon 5 position of the cytosine ring.
2. In mammals, DNA methylation is crucial for normal development, cellular differentiation, and X-chromosome inactivation in females.
3. Abnormal DNA methylation patterns are associated with various diseases, including cancer, where hypermethylation can silence tumor suppressor genes.
4. DNA methylation can be inherited through cell divisions, allowing for stable gene expression changes across generations without altering the DNA sequence.
5. Methylation patterns can be influenced by environmental factors such as diet, stress, and exposure to toxins, linking lifestyle choices to gene regulation.

Review Questions

• How does DNA methylation contribute to gene regulation within cells?
  • DNA methylation contributes to gene regulation by adding methyl groups to specific sites on the DNA molecule, particularly at CpG dinucleotides. This modification can prevent transcription factors from binding to the promoter regions of genes, effectively silencing those genes. As a result, DNA methylation serves as a key mechanism that cells use to control which genes are expressed and when, impacting cellular function and identity.
• Discuss the role of DNA methylation in epigenetics and its implications for development and disease.
  • In epigenetics, DNA methylation plays a central role by enabling reversible modifications that affect gene expression without changing the underlying genetic code. During development, precise patterns of DNA methylation are established to regulate gene expression necessary for differentiation into various cell types. However, alterations in these patterns can lead to disease states, such as cancer, where abnormal methylation may silence critical tumor suppressor genes or activate oncogenes, emphasizing the importance of maintaining proper methylation patterns for health.
• Evaluate the potential consequences of environmental influences on DNA methylation and how they may affect long-term health outcomes.
  • Environmental influences such as diet, stress, and exposure to pollutants can significantly impact DNA methylation patterns. These changes can lead to altered gene expression that may predispose individuals to various diseases over time. For instance, poor dietary choices might result in hypomethylation of genes related to metabolism or immune function, increasing the risk for obesity or autoimmune disorders. Understanding these relationships highlights the complex interplay between our environment and genetic regulation, suggesting that lifestyle modifications could potentially reverse harmful methylation changes and improve health outcomes.

Related terms

Epigenetics:

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

Histone modification: The process of adding or removing chemical groups to histone proteins, which can affect how tightly or loosely DNA is wrapped around them and thereby influence gene accessibility and expression.

Gene silencing: The process by which a gene's expression is inhibited or completely turned off, often as a result of DNA methylation or other epigenetic modifications.