Prompt 2: "Unnatural Selection"(see page 254)

Prompt 2: "Unnatural Selection"(see page 254)

How has human behavior and actions caused certain traits to be selected for in a given population of organisms? Are these traits necesarily a selective advantage in a natural, non-disturbed environment? (Use the Bighorn ram and the Atlantic cod as examples)

Fossil Genes Versus Immortal Genes

Carroll classifies fossil genes as those that have evolved "as a consequence of the continuing action of mutation, over time, in the absence of natural selection," (123). Mutations and sexual recombination create variation within the genetic pool of a population. New alleles originate only by mutation and these can be either synonymous or non-synonymous. As a result, some mutations can cause redundancy and others have no significant impact. However, mutations that cause the erosion of genes contribute to fossil genes. With such fossil genes being left behind with the relaxation of natural selection, many "injurious variations," as Darwin would have stated, will become rampant. Are such "junk" fossil genes truly "injurious" if they (can) create new alleles over time? Are fossil genes only eroding away just as Carroll states? Is it possible to have a once functional gene become a fossil gene, and then the same fossil gene becomes new gene that has either an injurious or a beneficial effect? What if immortal genes became fossil genes-why or why can't it happen? Could fossil genes contribute to the creation, through mutations, of "new" immortal genes to last through future generations? Carroll uses the phrase "Use it or lose it." How does this affect immortal versus fossil genes as well as your response(s) to the previous questions? I urge responders to read Carroll 123 carefully as well as Campbell 454.

Color Blindness A Fossil Gene?

"Color blindness is common in humans-up to 8 percent of Caucasian males are color-blind due to abnormalities in their X-linked red/green opsin genes. However, in the wild, color blindness is very rare. A study of 3153 macaque monkeys revealed only 3 color-blind individuals (less than 0.1 percent). Given the high frequency of color blindness in humans (where color vision is certainly under less intense selection now, if at all) and the low frequency of color blindness in the wild macaque, this suggests that selection is maintaining color vision in these monkeys and other trichromatic species," (Carroll 105). To review and understand why a male is more likely to receive the mild disorder (color-blindness), please read Campbell page 278.

If color blindness is increasing, albeit a rare disorder inherited as a sex-linked trait, why has natural selection relaxed (Carroll 123) upon these genes (opsins MWS and LWS) that lead to the development of color vision? How could natural selection contribute to creating these genes into fossil genes? Could natural selection be relaxed more upon sex-linked genes causing greater disruptions through evolutionary history because males receiving one copy of their X-chromosome from their mother could receive disorders much more easily?

Most mammals are nocturnal and thus the need for color vision is not truly a selective advantage as opposed to having rhodopsin (Caroll 123-124). If humans are diurnal, why is there a greater loss of color vision as it may provide a selective advantage?

Gene transfer from Fish to Chimp

According to Sean Carroll, "The three opsin genes of humans (SWS, MWS, and LWS) are also present in chimpanzees and other apes. However, most other mammals have just two opsins and genes, while birds and fish have four or more."
Amy the Mad Scientist has the embryo of a chimpanzee (in G0 state) and a fish with 4 opsins. Amy knows the DNA sequence for the genes that code for all 4 fish opsins, as well as the 3 opsins in the chimpanzee, but she doesn't know where these genes are found in the respective genomes. Amy wants to substitute the 3 opsin genes in the chimpanzee with the 4 opsin genes in the fish, so that she can observe the mutant chimp for further studying. How will she get about this?
Please be very thorough in your response. Subsequent responses following the first should build upon the pervious response, so that in the end, we have a very detailed process of how Amy should do this...

Symbiotic Relationships...

At the beginning of Chapter 4, Sean Carroll describes the colobus monkey and its digestion. "Bacteria in the colobus's gut help to digest the large bolus of leaves as it travels slowly through his digestive system, and unique enzymes break down key nutrients that are released from the bacteria". What type of symbiotic relationship is this? Why?
In addition, identify and explain each type of symbiotic relationship, with an example for each. For each example, explain how the relationship is selectively advantageous for at least one organism involved.

Prompt 1: Form and Function

Discuss how the form (protein structure) of an opsin affects the function of the opsin, specifically referrencing various opsin proteins. Then, evaluate the functions of the various opsins as a selective advantage for a given organism.

Transposon

In the course of 525 million years of vertebrate evolution, the opsin gene has gone from 5 opsins in lampreys to 4 opsins in fish, reptiles, and birds to 2 opsins in non-primate mammals and finally to 3 opsins in primates. Does the high frequency of the opsin gene’s deletion and duplication during vertebrate evolution indicate that the opsin gene is a transposon? Discuss other incidents where the duplication and/or modification genes contributed to an organism’s success.

Color Vision - Good or Bad?

The presence of five opsin genes in primitive lampreys and four opsin genes in birds, reptiles, and fishes indicates that color vision evolved early on in vertebrate evolution. Non-primate mammals, higher up on the evolution tree than fish or reptiles, only have two opsins. Thus fishes, reptiles, and birds have full color, trichromatic vision while non-primate mammals have dichromatic vision and can only see the visible spectrum from blue to yellow (no red or green). Sean Carroll postulates that the loss of color vision in non-primate mammals was due to the nocturnal lifestyle of early mammals. Color vision might have been unnecessary but was it so detrimental that natural selection would eliminate it from the early mammalian branch? Wouldn’t it have been more advantageous for mammals to fine tune their three or four opsins to fit their nocturnal needs rather than eliminate opsins?