On pages 155-157, Dr. Moalem introduces the idea of epigenetics
and its relation to Big Idea 1 (The process of life drives the diversity and
unity of life). He uses it when discussing overweight children as an effect of
their mothers’ possible eating habits.
First, explain the process of evolution and the inheritance
of DNA. Be sure to explain adaptation and specific how this plays into
evolution. Then, briefly explain epigenetics. How does epigenetics differ from
the traditional evolutionary cycle?
Next, find research from outside sources that supports
epigenetics. How does this research support epigenetics (explain why the
experiment would be proof of epigenetics)? Also find research that shows
possible implications of epigenetics. Can epigenetics be used and manipulated
to benefit humans? Can it be harmful?
Finally, try to connect previous AP Biology units together
using epigenetics. For example, how would epigenetics affect gene expression?
What does epigenetics mean for inheritance patterns? How do ‘tags’ affect
genotype and phenotype? What does this do to protein synthesis? Create a paragraph
or so that connects these ideas (and any others) that can be followed like a
flow-chart, relating each idea together and to epigenetics in a constructive
and logical order.
(Morgan Eisenstot – meisens4@students.d125.org)
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ReplyDeleteIn the traditional inheritance schematic, 23 chromosomes from the father are combined with 23 chromosomes from the mother, and the resulting 46 chromosomes determine the offspring’s phenotype. When an allele gives an individual an advantage in his quest to survive and reproduce, he will be more likely to do so, and others will likely be unable to do so; over time, the beneficial allele spreads throughout a population, increasing in frequency with each subsequent generation. This is the process of Natural Selection.
ReplyDeleteRecently, scientists have discovered that the genome (DNA sequence) of an organism is not the only thing that affects the phenotype. Phillip Hunter of Prospect Magazine mentions that honeybee larvae become drones or queens based on their interactions with other honeybee larvae; their genomes are identical! (http://web.archive.org/web/20080501094940/http://www.prospect−magazine.co.uk/article_details.php?id=10140) According to an article on ScienceDaily.com, a honeybee larvae becomes queen by eating a substance known as royal jelly, which affects the histone code of the bee. Histones are the proteins around which DNA is wrapped, and if DNA is wrapped tightly around a histone, it is unlikely to be expressed because RNA transcriptase cannot wedge itself in between the genetic code and the protein. Royal jelly alters how tightly certain sequences of DNA are bound to their histones. The mechanism of this manipulation is unclear, but once the histone code has been altered, DNA is expressed in an alternative way. (http://www.sciencedaily.com/releases/2012/12/121211101942.htm) A study cited in the first article demonstrates clearly that epigenetic markers can be inherited just as easily as genetic code itself. Of 5000 fathers who took place in the survey, 166 had begun smoking during the “slow-growth” period (ages 9-12) and their sons demonstrated high rates of obesity by the time they were 9 years old. Again, the exact mechanism of epigenetic alterations in unclear; it is thought that certain methyl groups bind to the promoter region of DNA and block transcription factors that would help RNA transcriptase bind to the strand.
The end result of epigenetic inhibition (or stimulation) of genes is well understood. When DNA bound to a histone is acetylated, a COCH3 group is added to the histone protein, which changes shape so the DNA is bound less tightly and RNA transcriptase can enter and transcribe the DNA. After transcription, the newly visible genetic information is translated by mRNA, tRNA, and ribosomes. DNA methylation has the opposite effect, the affected sequence of DNA is not transcribed by RNA transcriptase, nor is it translated by the rest.
The budding scientific realm of epigenetics has startling implications for the decades old theory of evolution. The last example demonstrated clearly negative effects of epigenetic, but positive lifestyle choices leave epigenetic markers just as clear as negative ones. According to an article on Viewzone.com, in a European farming village, those that lived through and reproduced in years of famine lived longer lives by 32 years – and so did their children. (http://www.viewzone.com/morphogenetic22.html) While inflicting famine on oneself is not going to be a favorite of physical or mental health experts, this example demonstrates at least that epigenetic markers can have beneficial results as well as negative results. And these benefits are favored by natural selection in the same way useful genomic changes are favored by natural selection; the kids of famine parents lived longer lives and were able to generate more offspring, so the beneficial epigenetic markers spread throughout the population.