Shenk proposes that genes should be thought of as "volume knobs and switches...a giant control board inside every cell of your body," and that "Many of those knobs and switches can be turned up/down/on/off at any time - by another gene or by any minuscule environmental input. (p 19)" Can this idea of volume control with regards to personal skills/abilities (the prospect of being a genius) be related to the trp and lac operon in E. coli? Specifically focus on the lac operon, which has an "on/off" switch that depends on the presence of lactose, yet also has what can be considered a "volume" switch that depends on the level of cyclic AMP present, which determines the rate of gene transcription for the production of enzymes (Campbell p 355). But since the lac operon is present only in prokaryotes, are there similar gene regulation mechanisms that deal with both on/off as well as volume control in humans? It is preferable for you to discuss a gene regulation mechanism that involves dexterity or intelligence, either of which could contribute to the creation of a genius. In your discussion, relate the regulation system to the biology theme of either continuity and change or homeostasis.
-Mark Zhang (mzhang59@gmail.com)
If there happens to be plentiful milk (lactose) but low glucose in the human colon, E. coli undergo positive gene regulation. Cyclic AMP (cAMP) accumulates and binds to the catabolite activator protein (CAP), stimulating gene transcription (Campbell 355). Gene regulation in humans is similar in the fact that it is also their environment that stimulates the gene expression. In fact, this explains the existence of prodigious savants: they had severe impairments due to some state of the environment, but it stimulated new gene expression to compensate which resulted in their extraordinary abilities (89). Never mind severe impairments—humans can also induce gene expression if they put themselves in the right environment to. This is the core of David Shenk’s thesis as he quotes Anders Ericsson: “‘When individuals deliberately push themselves beyond the zone of relative comfort…, they [induce] an abnormal state for cells…[which] will trigger the activation [of] dormant genes within the cells’ DNA’” (69). Thus, depending on what environment, an individual has some influence over what their genes expression. First, there’re gene regulating mechanisms.
ReplyDeleteExamples of human gene regulation mechanisms include histone acetylation and histone methylation. In histone acetylation, acetyl groups (-COCH3) are attached to lysines in histone tails. This neutralizes the positive charges in lysines that had promoted a compact folding of chromatin. The chromatin loosens, and transcription proteins have easier access to genes for transcription. Histone methylation functions in the complete opposite way: methyl groups promote condensation of the chromatin, discouraging gene transcription (Campbell 358). The use of histone acetylation and methylation can be a tricky—hyperacetylation is linked to cancer while early methylation of genes is the culprit for developmental brain disorders (http://neurosciencenews.com/environment-gene-regulator-brain-executive-hub-dna-methylation/). Thus, there needs to be an optimal amount of histone acetylation (gene expression) and histone methylation (gene repression). In terms of promoting intelligence, the optimal state is the increased of histone methylation and decreased of methylation of this gene: STX1A.
A study from the University of Utah found that the brain gene—STX1A—could possibly be the “intelligence gene”. Patients with Williams Syndrome (the deletion of 24 genes from chromosome 7) had an increased level of intelligence (measured with standardized tests) with the increased gene expression of STX1A. Researchers believe this is the case because STX1A is involved in the speed of electrical signals from one neuron to the next. Thus, if the gene regulation mechanism of STX1A was histone acetylation, there could be an increase in levels of intelligence—perhaps enough to constitute a “genius”.
PART 1
Linda Xu (lindaxu22hotmail.com)
The following regulation mechanisms discussed so far can be connected to the theme of continuity and change. It relates to “continuity” since as Campbell says, “the chromatin modifications…do not entail a change in the DNA sequence, yet they may be passed along to future generations of cells. Inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence is called epigenetic inheritance” (Campbell 358). Now, not only is DNA inherited but also epigenome changes. Thus, mechanisms of histone acetylation and histone methylation can be passed down. These regulation mechanisms also related to “change”. A mutation such as the deletion of 24 genes in Williams Syndrome will incite a method of compensation. The impairment caused by Williams Syndrome results in this form of compensation: increased use of the amygdala, which is associated with social and emotional processing. Thus, people with Williams Syndrome are extremely sociable, use emotionally vivid language, and are masters of facial expressions (http://news.stanford.edu/news/2009/january28/med-williams-012809.html). Histone acetylation and histone methylation could have a role in developing these characteristics—either promoting or inhibiting certain gene expressions.
ReplyDeletePART 2
Linda Xu (lindaxu22@hotmail.com)