Dr. Moalem also mentions findings that identical twins’ methylation patterns diverged as they grew older.
First, provide a specific example of a behavior or
environmental factor that can potentially lead to cancer (you can use an
example from the book or find another) and explain how methylation is involved.
Be sure to define and explain hypermethylation.
Next, explore the benefits of studying identical twins’ genomes. How can this
contribute to our knowledge of methylation patterns? In the long run, how can
more knowledge of methylation further our methods of diagnosing and treating
cancer?
(Sanika Bhargaw, sbharga4@students.d125.org)
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ReplyDeleteSam Rhine explained during his Genetic Update Conference that common diseases (diseases that have no Mendelian inheritance pattern and whose chromosomes and karyotype are fine) have both a genetic component and an environmental component. Because environmental factors can be involved in being diagnosed with a common disease, common diseases are known to be multifactorial. Sam Rhine pointed out an example, saying that being diagnosed with adult II diabetes is usually due to a 55% heritability/genetic factor and a 45% environmental influence. Dr. Moalem explains this idea on pages 170-172 - the idea that one of two identical twins (who both have the same exact DNA) was diagnosed with breast cancer later in her life while the other was not due to geographical separation and vulnerability to different environmental pollutants. It is possible that Eleanor was diagnosed with breast cancer because she was exposed regularly to smoke in the big city where she lived later in her life; therefore, smoke could be an example of an environmental factor that could potentially lead to symptoms of breast cancer. Eleanor’s daily exposure to smoke may have triggered a set of enzymes to methylate (add methyl groups to) certain bases in her DNA and thus repress the process of transcription and gene expression. It is important to note that once methylated, genes usually stay that way through successive cell divisions in a given individual. Therefore, if the wrong genes were turned off (in Eleanor’s case, they were), this could lead to the individual being diagnosed with a common disease (in Eleanor’s case, she started to develop signs of breast cancer). Thus, DNA methylation as a result of environmental factors affects gene regulation in eukaryotic cells and can potentially have detrimental effects on an individual. Hypermethylation just means an increase in the epigenetic methylation in DNA, so this means that genes in DNA are continually turned off. It is important to study identical twins’ genomes because we can see that although they have the exact same genetic code (DNA), throughout the course of their lives, they develop different epigenetic patterns (e.g. Histone Acetylation or DNA Methylation) and therefore, contrary to popular belief, DNA is not fate. By continuing to understand methylation, scientists can try to find out how to prevent certain essential genes from turning off (genes that are crucial in preventing common diseases like cancer). By allowing these genes to turn back on, scientists can help treat cancer patients.
ReplyDelete(Tina Moazezi, tmoazez4@students.d125.org)