A recent estimate of the rate of base substitutions atSNP loci is about 1 × 10−8 per nucleotide pair pergamete.a. Based on this estimate, about how many de novomutations (that is, mutations not found in the genomes of your parents) are present in your own genome?b. Where and when did these de novo mutations inyour genome most likely occur?c. It has been calculated that each sperm made in a25-year-old man is the result on average of about300 rounds of cell division, starting with the firstmitotic division of the male zygote. In contrast,each mature oocyte found in a 5-month-old femalehuman fetus is the result of about 25 rounds of division, starting with the first mitotic division of thefemale 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)?
Oogenesis
The formation of the ovum (mature female gamete) from undifferentiated germ cells is called oogenesis. This process takes place in the ovaries (female gonads). Oogenesis consists of three stages known as the multiplication phase, growth phase, and maturation phase.
Cell Division
Cell division involves the formation of new daughter cells from the parent cells. It is a part of the cell cycle that takes place in both prokaryotic and eukaryotic organisms. Cell division is required for three main reasons:
A recent estimate of the rate of base substitutions at
SNP loci is about 1 × 10−8 per
gamete.
a. 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?
b. Where and when did these de novo mutations in
your genome most likely occur?
c. 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)?
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