DNA methylation

Definition

DNA methylation is a biochemical process involving the addition of a methyl group (CH₃) to the DNA molecule, primarily at cytosine residues in the context of CpG dinucleotides. This modification plays a crucial role in regulating gene expression, influencing processes like genomic imprinting, X-chromosome inactivation, and the suppression of transposable elements. By altering the accessibility of DNA to transcription factors and other regulatory proteins, DNA methylation serves as an essential mechanism in cellular differentiation and development.

5 Must Know Facts For Your Next Test

1. DNA methylation is predominantly found at CpG sites where a cytosine is followed by a guanine, and this modification can lead to gene silencing.
2. Methylation patterns can be inherited through cell division, which allows for stable gene expression states during development.
3. The enzyme DNA methyltransferase is responsible for adding methyl groups to DNA, while demethylases can remove them, allowing for dynamic regulation of gene expression.
4. Abnormal DNA methylation patterns are associated with various diseases, including cancer, where tumor suppressor genes may become silenced due to hypermethylation.
5. In plants and some animals, DNA methylation is also involved in regulating transposable elements, preventing them from becoming active and disrupting genomic integrity.

Review Questions

• How does DNA methylation impact gene expression and what are the mechanisms involved?
  • DNA methylation impacts gene expression primarily by adding methyl groups to cytosines within promoter regions of genes, making the DNA less accessible to transcription factors. This process often leads to the silencing of genes, preventing their transcription into mRNA. The mechanisms involve the recruitment of repressive proteins that further modify chromatin structure, thereby reducing the likelihood of transcription occurring.
• Discuss the relationship between DNA methylation and epigenetics, highlighting how environmental factors can influence this process.
  • DNA methylation is a key component of epigenetics as it involves heritable changes in gene expression that do not alter the DNA sequence itself. Environmental factors such as diet, stress, and toxins can influence DNA methylation patterns by altering the activity of enzymes responsible for adding or removing methyl groups. This interaction illustrates how external conditions can shape an organism's genetic expression over time without changing its genetic code.
• Evaluate the implications of abnormal DNA methylation patterns in human diseases, particularly cancer.
  • Abnormal DNA methylation patterns have significant implications for human diseases like cancer. In many cancers, tumor suppressor genes become hypermethylated, leading to their silencing and allowing unchecked cell growth. This change in methylation status can serve as a biomarker for cancer diagnosis and prognosis. Moreover, understanding these patterns opens up potential therapeutic strategies aimed at reversing abnormal methylation to restore normal gene function.

Related terms

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

Histone modification: The addition or removal of chemical groups on histone proteins, which can affect chromatin structure and influence gene expression, often working in concert with DNA methylation.

Transcription factors: Proteins that bind to specific DNA sequences to regulate the transcription of genes, their activity can be modulated by DNA methylation.