Frêsh Fish

Sunday, March 16, 2014

Notes on Genetics

23 vs. 24
Humans have 23 pairs of chromosomes. Chimpanzees and other Great Apes have 24 pairs of chromosomes. Man is thought to have shared a common ancestor with the chimpanzees 5,000,000 million years ago.

Lack of Genetic Variability in Humans relative to other Primates

The term "genetic variability" is not well defined in discussions of the difference between genetic variability of human beings relative to other life forms. It is unclear if the difference between individuals in the various groups being compared is in the composition of their genes - protein coding regions - or in their Junk DNA.

A question I am now considering is how sensitive is a protein to its amino acid representation? Can extra amino acids be included within the linear nucleotide sequence without influencing the production of a protein - perhaps just skipped over the unneeded nucleotides? Another way of stating this is, is there Junk DNA within the protein coding sequence?

"Humans generally are highly inbred - I remember reading somewhere that two chimpanzees from the same forest may differ more from each other than the furthest removed human populations. There is also a lot of variation between various human groups - Africans are generally the most diverse and East Asians the least. Ashkenazi Jews are so inbred that they are basically all related to each other as fourth or fifth degree cousins.

Cheetahs are so inbred that skin can be transplanted between individuals with no chances of rejection. This of course has drawbacks in form of poor adaptability, very low survival rates for kittens and being more prone to diseases."

Comparison of Genes - Human vs. Chimpanzee

When comparing the DNA of humans and chimps there are 2 conflicting statements. One strain of thought emphasizes how different the genetic makeup is of humans and chimps. Stating that humans have a lot less genetic variability than chimpanzees. The other statement focuses on how similar the DNA of humans and chimps are.

Here is a very informative letter published in Nature magazine - Unexpectedly Large Difference in Y Chromosome of Human in Comparison to Chimpanzee

This large difference in the Y Chromosome of Human in Comparison to Chimpanzee is supported by the diagram above that compares the chromosomes of Humans and Chipanzees. The Y chromosome is the last chromosome in the series. In each set the human chromosome is on the left and the chimpanzee is on the right. In the diagram the human Y chromosome is much larger than the chimpanzee.

Junk DNA

Cell - Nucleus - DNA - Nucleotides - C,A,T,G - code for amino acids and random (Junk DNA) - amino acids code for proteins. Genes are sequences on the chromosome that code for proteins. DNA = genes + Junk. The term genome refers to all nucleotides - protein coding and Junk.

98.5% of the human genome codes for junk. Only 1.5% of the information contained in the human genome codes for proteins = genes.


In the article Initial sequencing and analysis of the human genome Nature 1/9/2001 I found this statement very interesting - "The mutation rate is about twice as high in male as in female meiosis, showing that most mutation occurs in males." I am actually surprised that male mutation rate is not much higher.

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