5) A recent estimate of the rate of base substitutions at SNP loci is about 1x10

Question

5) A recent estimate of the rate of base substitutions at SNP loci is about 1x10-8 per nucleotide pair per gamete.

Based on this estimate, about how many de novo mutations (that is, mutations not found in the genomes of your parents) are present in your own genome?

Where and when did these de novo mutations in your genome most likely occur?

It has been calculated that each sperm made in a 25-year-old man is the result on average of about 300

rounds of cell division, starting with the first mitotic division of the male zygote. In contrast, each mature oocyte found in a 5-month-old female human fetus is the result of about 25 rounds of division, starting with the first mitotic division of the female zygote. What bearing do these calculations have on the estimate of the rate of base substitutions in humans, and on your answer to part (b)?

Explanation / Answer

In a double strand of DNA, there are 6*10^9 base pairs. So, there are 6 billion positions where SNP mutation can occur.

Number of base substitution at one loci = 1*10^-8

Number of base substitution at 6 billion loci = 6* 10^-8 * 10^9 = 60 (So, there are chances of having 60 de novo mutations)

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