Journey of Man Video questions. Please answe all 5 questions. 1. How are genetic

Question

Journey of Man Video questions. Please answe all 5 questions.

1. How are genetic polymorphisms used to distinguish populations?

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2. Why is the Y chromosome (and not some other chromosome) particularly useful in this endeavor?

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3. What evidence is there that Africans, certain Indians and Australian aborigines are related?

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4. Where does Dr. Wells suggest that the ancestors of Europeans came from? Why did they move?

Explanation / Answer

Ans 1: Genetic polymorphisms is defined as presence of several phenotypes in the same population, some DNA tools or markers like RFLP, mini- and microsatellite variation, or DNA sequences are helpful in distinguish populations. Genetic polymorphisms, through multiple alleles at individual loci, provide a mechanism to tag a gene or a piece of DNA, which is a powerful tool for a variety of investigations. In Genetic polymorphisms studies a locus should contain two or more alleles and most common allele should have frequency of > 90%. For example two alleles say ‘A and a’ in a random mating population produced three genotypes say AA (90%), Aa (9.5%), aa (0.5%). In inbreeding population genetic polymorphisms occur in increased levels in homozygous genotypes and to a less extent in heterozygous genotypes by this data we can distinguish polymorphism in populations.

Ans 2: Y chromosome is small, gene-poor and rich in repetitive sequence. Their non-sex-specific partners, the X chromosome having more genes autosome like in form and content, and in many cases undergo dosage compensation to equalize gene activity between the sexes. Genetic markers palindromes (regions of DNA in which the sequence of nucleotides are identical with an inverted sequence in the complementary strand) on the non-recombinant region of the Y chromosome have been used. These palindrome markers on Y chromosomes are not much changed hence provide the human migration and the clues to the past. These palindrome markers allow for the reconstruction and tracing of ancient human migration routes. The Y chromosome has become such a research interest that the National Geographic Society is undertaking its most ambitious project, the Genographic project. Under the direction of population geneticist, Dr. Spencer Wells, and at a cost of 40 million dollars over five years, the Genographic project is establishing eleven DNAsampling centers with the goal of collecting over 100,000 DNA samples worldwide.

Ans 3: All humans including Africans, Europeans, Indians and Australian aborigines carry a Y chromosome marker known as M168. This marker mutated or SNPs formed and gave rise to C-M130, this is direct evidence.

Ans 4: In his book The Journey of Man, Wells shows that Europe's ancestry derives mainly from people in that continent around 30,000 years ago; not from early agriculturalists in the Middle East. But there was an invasion of Aryans from the steppes, which imposed the Indo-European languages on Europe and northern India. Spencer Wells discovered a genetic marker, M17, which is the signature of the Aryan invaders from the steppe into east & central Europe and northern India. He says that people moved out of Africa (because Africa getting dried this is due to heavy ice sheets in northern hemisphere, ice age) in to middle east then on to central area and further. Back migrations happened in to Europe from central Asian steppes as recent as 30-35000 years because by that time ice melted in Europe .

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