CpG

Definition

CpG refers to a dinucleotide sequence where a cytosine (C) is followed by a guanine (G) in the DNA strand, connected by a phosphate group. These sites are significant because they are often located in promoter regions of genes and play a crucial role in gene regulation, particularly through the process of DNA methylation, which can lead to gene silencing or activation.

5 Must Know Facts For Your Next Test

1. CpG islands are regions with a high frequency of CpG sites and are typically found near gene promoters, making them critical for the regulation of gene expression.
2. Methylation of CpG sites can lead to transcriptional repression, where genes are turned off, contributing to cellular differentiation and development.
3. In cancer biology, abnormal methylation patterns at CpG sites can lead to the silencing of tumor suppressor genes, playing a significant role in tumorigenesis.
4. The presence or absence of methyl groups at CpG sites can be inherited through cell division, contributing to epigenetic inheritance.
5. Research shows that environmental factors, such as diet and stress, can influence the methylation status of CpG sites, thus impacting gene expression.

Review Questions

• How does DNA methylation at CpG sites influence gene expression?
  • DNA methylation at CpG sites is a key mechanism that can repress gene expression. When a methyl group is added to the cytosine in a CpG dinucleotide, it often prevents transcription factors from binding to the DNA, blocking the transcription process. This modification plays an essential role in cellular processes like differentiation and development by regulating which genes are active or silent in specific cell types.
• What is the significance of CpG islands in relation to transcription factors and gene regulation?
  • CpG islands are crucial because they are often located within or near the promoter regions of genes. Transcription factors bind to these areas to initiate transcription; however, when these sites are heavily methylated, it can prevent the binding of transcription factors. Therefore, the methylation status of CpG islands directly impacts gene regulation and expression, affecting how genes respond to various signals.
• Evaluate how abnormal methylation patterns at CpG sites may contribute to cancer development.
  • Abnormal methylation patterns at CpG sites can lead to the silencing of critical tumor suppressor genes that normally help regulate cell growth and prevent tumor formation. When these genes are turned off due to excessive methylation, it disrupts normal cellular function and allows uncontrolled cell proliferation. This process highlights the importance of epigenetic mechanisms in cancer development, as alterations in CpG site methylation can significantly impact cellular behavior and contribute to malignancy.

Related terms

DNA Methylation: A biochemical process where a methyl group is added to the DNA molecule, typically at CpG sites, affecting gene expression without altering the DNA sequence.

Transcription Factors: Proteins that bind to specific DNA sequences and regulate the transcription of genetic information from DNA to mRNA.

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