The Argument-
According
to Shenk, “genes play a crucial role throughout the process. Their
information is translated by other actors in the cell and influenced by a
wide variety of other signals coming from outside the cell” (26). He
uses the experiment done by Rod Cooper and John Zubek on rat
intelligence showing that while the “Maze-bright” rats did better in
normal environments of solving the maze than the “Maze-dull” rats, the
“Maze-bright” rats nearly equally as bad as the “Maze-dull” rats in a
confined environment. Given that the normal environment is what the rats
are used to living in, is it possible that the genes for intelligence
have turned out this way due to evolution? In other words, if the rat’s
natural habitat is the normal environment, then could the genes for
intelligence of that species be limited through natural selection for
optimal intelligence in normal conditions? Consider that genes are
acquired by parents by inheriting chromosomes (Chapter 13.1). If the
genes are only to be inherited from the parents, then those who do not
reproduce do not have offspring that have that individual’s genes, and
if one gene vanishes through natural selection, then the trait that the
gene codes for is lost. Could this, the lack of a gene for intelligence
in unnatural habitats, be a reason why these “Maze-bright” rats are not
able to solve mazes well when put in a confined environment? Are there
genes that only code for proteins in a very specific environment? Relate
your answer to the theme of evolution.
Matthew Yang (matt.y.yang2013@gmail.com)
Shenk says that "the more complex the trait, the further any one gene is from direct instruction" (26). Clearly, intelligence is quite possible the most complex trait possible as it continues to develop throughout a lifetime. Shenk also compares genes to "knobs and switches [that] can be turned up/down/on/off at any time--by another gene or by any minuscule environmental input" (19). Therefore, the expression of any trait will be differed depending upon the environment, even if the genes are identical. Clearly, the genome of the Maze-bright rats and the Maze-dull rats are different as they both performed very differently in the normal environment. This is most likely due to the fact that under normal environmental conditions, the Maze-bright rats' genes for intelligence are "turned up" while the Maze-dull rats' genes for intelligence are "turned...down". This difference in performance under normal environmental conditions may be due to a difference in lifestyles of the different strains of rats. The Maze-bright rat may commonly live near the influence of humans which required them to be able to react quickly in order to survive which caused the continuity of the same genes for intelligence as they allowed the rat to survive and reproduce. On the other hand, the Maze-dull strain may commonly live in a much more passive environment with very little external dangers. This is similar to the relationship between cephalopods and bivalves. Although both are classes of phylum Mollusca, their tremendous difference in lifestyle explains the huge differences in characteristics. Cephalopods have closed-circulatory systems and grasping tentacles to promote their active predatory lifestyles. On the other hand, bivalves have strong threads and a muscular foot to support their suspension feeder lifestyle (Campbell 680). This clearly also shows that the difference in intelligence is not entirely due to differences in genes, but also differences in environmental factors.
ReplyDeleteHowever, it is still highly likely that the genes for intelligence in the Maze-bright rats are passed down through evolution because the ability for these rats to perform extremely well when even raised in a normal environment is undoubtedly a selective advantage. However, it is also true that the Maze-dull rats are still surviving and reproducing which shows that the environment is not rigorous enough to eliminate the Maze-dull rats, along with their intelligence genes that are turned down under normal environmental conditions. Thus, these rats passed on a different set of genes for intelligence as their respective environment allows them to survive and reproduce. The reasoning for poor performance when raised in a restricted environment for Maze-bright rats is most likely due to the fact that the restricted environment does not demand high intelligence rather than the genes. There are not separate genes for intelligence in different types of environment, but the same set of genes that are amplified only as strongly as the environment demands of it. Therefore, it is quite clear as to why both strains of rats performed nearly the same when raised under the restricted environment as both strains did not have any environmental stimuli that required them to increase their intelligence.
There are many genes that only code for protein under specific environmental conditions. For example in prokaryotes, the gene for the enzyme β-galactosidase is only transcribed and translated if the sugar lactose is present in the prokaryotes environment (Campbell 354). Harvard School of Public Health says that, “genes influence every aspect of human physiology, development, and adaptation [and that] obesity is no exception” and also that “most humans probably have some genetic predisposition to obesity…but triggering the expression of an obesity-related phenotype generally requires some change in…environmental factors” (Harvard School of Public Health). http://www.hsph.harvard.edu/obesity-program/resources/genes-and-obesity/index.html Clearly, not all humans are obese; therefore, the genes that produce proteins related to obesity are only transcribed and translated when under specific environmental conditions.
ReplyDelete-Josh Choi (joshchoi95@yahoo.com)