Question

BIOCHEMICAL CONNECTIONS What does "epigenetics" mean?

Short answer

Epigenetics involves changes in gene activity without altering the DNA sequence, influenced by mechanisms like DNA methylation and histone modification.

Step-by-step solution

Understand the Root Words

The term 'epigenetics' derives from the Greek word 'epi,' meaning 'above' or 'over,' and 'genetics,' which refers to the study of genes. So, the word 'epigenetics' literally means 'above genetics.'

Define Epigenetics in Simple Terms

Epigenetics refers to changes in gene expression that do not involve alterations to the underlying DNA sequence. In other words, it’s the study of various factors and mechanisms that modify the activity of genes without changing the genetic code.

Mechanisms Involved

Common mechanisms of epigenetic changes include DNA methylation, histone modification, and non-coding RNA molecules. These mechanisms can turn genes on or off and influence how cells read genes.

Significance of Epigenetics

Epigenetics has significant implications in various fields, including development, biology, and medicine. It helps explain how environmental factors, such as diet and stress, can affect gene activity and contribute to conditions like cancer and neurological disorders.

Key concepts

gene expression

Gene expression is the process in which information from a gene is used to create a functional product, usually a protein. It's an essential mechanism that allows cells to perform their specific functions.
Gene expression involves two key stages: transcription and translation.

• In transcription, the DNA sequence of a gene is copied into messenger RNA (mRNA).
• During translation, the mRNA is used as a template to build a protein. This occurs at the ribosome.

Various factors, like transcription factors and epigenetic mechanisms, can regulate gene expression.
If a gene is not expressed properly, it can lead to diseases. Epigenetic mechanisms play a critical role in controlling gene expression to ensure healthy development and functioning.

DNA methylation

DNA methylation is an epigenetic mechanism involving the addition of a methyl group (CH3) to the DNA molecule. This usually happens at cytosine bases next to guanine bases, commonly called CpG sites.
This modification can repress gene activity without altering the DNA sequence itself.

• In many cases, increased DNA methylation at a gene promoter region leads to gene silencing.
• Methylation is essential for normal development and plays a role in genomic imprinting, X-chromosome inactivation, and more.

Abnormal patterns of DNA methylation are associated with various diseases, including cancer, where they may contribute to the inappropriate activation or silencing of genes.
Understanding the role of DNA methylation helps in diagnosing and treating these diseases.

histone modification

Histones are proteins that DNA wraps around to form chromatin, which makes up chromosomes. Histone modification is an epigenetic mechanism that affects how tightly or loosely DNA is wound around these proteins.
Types of Histone Modifications include:

• Acetylation: Addition of acetyl groups generally makes DNA more relaxed, promoting gene expression.
• Methylation: Addition of methyl groups can activate or repress gene expression depending on the specific histone and location.

These modifications are accomplished by various enzymes. For example, histone acetyltransferases (HATs) add acetyl groups, while histone deacetylases (HDACs) remove them.
The pattern of histone modifications, known as the 'histone code,’ provides another layer of regulating gene expression and can influence cellular processes and disease development.

non-coding RNA

Non-coding RNAs (ncRNAs) are RNA molecules that aren't translated into proteins but play critical roles in regulating gene expression.
Types of Non-Coding RNAs include:

• MicroRNAs (miRNAs): Small RNAs that can bind to mRNAs and prevent their translation, effectively silencing specific genes.
• Long non-coding RNAs (lncRNAs): Larger RNA molecules that can modulate gene expression in various ways, including chromatin remodeling and transcript stability.

These ncRNAs contribute to controlling diverse biological processes like development, differentiation, and the stress response.
Mutations or misregulation of ncRNAs have been linked to diseases such as cancer, highlighting their importance in gene regulation.

environmental factors and gene activity

Environmental factors play a critical role in modulating gene activity through epigenetic mechanisms. These influences can lead to changes in gene expression without altering the underlying DNA sequence.

• Diet: Nutrients and bioactive food components can affect DNA methylation and histone modifications, impacting gene expression patterns.
• Stress: Psychological stress can lead to epigenetic modifications that affect gene expression in the brain and other tissues.
• Exposure to toxins: Chemicals and pollutants can also cause epigenetic changes that may lead to diseases like cancer.

Such environmental factors can have long-lasting effects on gene activity and can even be passed to offspring, affecting their health and development.