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Lecture 5

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University of Toronto St. George

Lecture Five and Six -Looking at the number of genes in organisms, there demonstrates no clear correlation between biological complexity and genes within a DNA -There is very little difference between human individuals within a species, Craig Venter and Francis Collins remarked that biological determinism is not what creates differences, rather the environmental factors influenced phenotype development -Scientists conclude it was wrong however, and there does not need to be many genes for organisms to differ -Differences between species, in both how they survive and so-on, is not correlated with the amount of differences observed -Frogs for example, differ very little in lifestyle, yet are any more years apart than Chimpanzees and Humans are -Discovered are a set of genes found in all animals, known as “Hox Genes”, which are very important in the function of and regulation of other genes -These genes being common in all animals, is purpoted to have arisen in a period of tremendous diversification -An example is HOX C8, which switches off genes involved in the development of the verterbrae -The differences between a mouse and a chicken vertebrae, are due to the turning on and turning off of the development of this vertebrae -This gene tweaks the expression of structural genes, without altering said gene itself -The discovery of HOX genes means rather than there being a quantitative number of genes accounting for differences, it is instead a small number of genes that alter other genes which contribute to the evolution of complex structures -Sean Carroll had studied the spots on a fruit fly, and his discovery concerned what had caused the black color and spots among fruit flies -One gene, “yellow” is responsible for the expression of color in different places on the same organism -This is a case of pleiotropy, due to this one gene affecting different parts or coloration on the fly body, the wing and the abdomen being altered -Allometric growth refers to differences in the rate and timing of the development of an organism -In the fetus of a chimp and a human,
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