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Biology
Epigenetics & Environment
How Lifestyle Marks the Genome
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Epigenetics is the study of changes in gene activity that do not alter the DNA sequence itself. It helps explain how cells with the same genetic code can become different cell types, such as skin cells, neurons, or muscle cells. These changes matter because they influence growth, health, behavior, and disease risk. Epigenetics also shows how the environment can affect which genes are turned on or off.
Key Facts
- Epigenetics changes gene expression without changing the DNA base sequence.
- DNA methylation often reduces gene expression by adding methyl groups to DNA.
- Histone acetylation usually increases gene expression by loosening DNA around histones.
- Gene expression is the process of using DNA information to make RNA or protein.
- Environment factors such as diet, stress, toxins, sleep, and exercise can influence epigenetic marks.
- Some epigenetic marks can be copied during cell division, and a few may be passed to offspring.
Vocabulary
- Epigenetics
- Epigenetics is the study of chemical changes that affect gene activity without changing the DNA sequence.
- Gene expression
- Gene expression is the process by which information in a gene is used to make a functional product, usually RNA or protein.
- DNA methylation
- DNA methylation is the addition of methyl groups to DNA, often making a nearby gene less active.
- Histone
- A histone is a protein that DNA wraps around to help package genetic material inside the nucleus.
- Histone modification
- Histone modification is a chemical change to histone proteins that can make DNA more or less accessible for gene expression.
Common Mistakes to Avoid
- Saying epigenetics changes the DNA sequence is wrong because epigenetic marks affect how genes are used, not the order of A, T, C, and G bases.
- Assuming all epigenetic changes are permanent is wrong because many marks can change over time in response to development, lifestyle, or environment.
- Thinking one environmental factor always causes one exact gene response is wrong because gene expression depends on cell type, timing, dose, and many interacting signals.
- Ignoring histones is wrong because gene activity is controlled not only by DNA methylation but also by how tightly DNA is wrapped around histone proteins.
Practice Questions
- 1 A gene has high expression when its relative mRNA level is 100 units. After increased DNA methylation near its promoter, expression drops to 25 units. What percent decrease in expression occurred?
- 2 In a cell sample, 60 out of 200 copies of a gene are heavily methylated. What percentage of the gene copies are heavily methylated?
- 3 Explain why two identical twins can have different risks for a disease later in life even though they began with nearly identical DNA sequences.