Notes for D2.2.8 Examples of environmental effects on gene expression in cells and organisms - IB | RevisionDojo
D2.2.8 Examples of environmental effects on gene expression in cells and organisms Notes
DNA Methylation is a Response to Air Pollution
Air pollution, particularly fine particulate matter (PM2.5) and harmful gases like nitrogen dioxide (NO₂), has been shown to alter DNA methylation patterns.
Exposure to these pollutants triggers oxidative stress and inflammation, leading to epigenetic modifications in key genes.
Air pollution
Key Findings from Research
Hypermethylation of Tumor Suppressor Genes
Studies have shown that long-term exposure to air pollution can cause hypermethylation of tumor suppressor genes, silencing their expression.
This increases the risk of developing cancers such as lung cancer.
Hypomethylation of Pro-Inflammatory Genes
Inflammatory pathways are often activated by hypomethylation of genes involved in cytokine production.
People exposed to high levels of PM2.5 show increased activity in genes associated with chronic inflammation.
This is a precursor to cardiovascular and respiratory diseases.
Note
Children growing up in areas with high air pollution show altered methylation patterns in immune-related genes.
These changes increase their susceptibility to asthma by promoting an overactive inflammatory response.
Other Examples of Environmental Effects on Gene Expression
1. Diet
A diet rich in folate enhances DNA methylation, supporting normal development.
Folate deficiency, on the other hand, reduces methylation, potentially leading to neural tube defects during fetal development.
Hint
Folate, also known as vitamin B9, is a water-soluble B vitamin that helps with cell growth and function, especially in red blood cells.
Foods high in folate include dark green leafy vegetables, beans, nuts, fruits, and eggs.
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Questions
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Question 1
Recap question
During pregnancy, adequate folate intake supports normal fetal development by influencing DNA methylation. Which mechanism best explains this effect?
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Give an example of how environmental factors can influence gene expression.
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Note
Epigenetics refers to changes in gene expression that do not involve alterations to the underlying DNA sequence. These changes can be influenced by environmental factors and can affect how genes are turned on or off.
DNA methylation is a key epigenetic mechanism where methyl groups are added to DNA, typically silencing gene expression.
Histone modification involves chemical changes to the proteins around which DNA is wrapped, affecting gene accessibility.
Non-coding RNAs can also regulate gene expression at the epigenetic level.
AnalogyThink of epigenetic changes like adding bookmarks to a book - they don't change the words, but they influence which sections are easily accessible.
DefinitionEpigenetics is the study of heritable changes in gene function that do not involve changes in the DNA sequence itself.
