Nswer a. how many mutations are there per billion base pairs replicated in a human cell? b. how many new mutations arise every time a cell in your body divides? c. how many base pair differences (new mutations) are there between you and your parents? d. how many total base pair differences are there between you and just your mother? e. which relatives do you share 50% of your snps with? 25%? 12.5%? (three answers for each) f. approximately how many base pair differences are there between you and a random person? g. how many disease-causing mutations does each of us carry? h. define mosaicism, microchimerism, and chimerism.

a. The error rate of DNA replication is 1.0 × 10^-8  per base pair. This is considering that a human has approximately 3 billion base pairs where mutations can occur. However, this mutation is kept low by the proof-reading mechanism of DNA polymerases which are 99% efficient.

b. Given that the human genome is 3.2 × 109 bp, this means that there are on average 0.32 new substitutions every time the complete genome is replicated. In humans, there are about 30 cell generations between zygote and egg cells and about 400 cell divisions between a zygote and mature sperm. Thus, in males, the sperm cells have about 128 new mutations and the haploid egg genome has about 10 new mutations for a total of 138 new mutations in every new zygote.

c. Considering the above-mentioned mutation rates of approximately 1 and 2 mutations per 100 million base pairs between generations, then there will be approximately 130 mutations per generation. This means I will probably have about 130 different nucleotide bases from that of my parents.

d. Siblings at an average of 50%, grandparents at an average of 25%; aunts/ uncles at an average of 25%; and  first cousins at 12.5%.

f. You  are approximately different from the other random person by one SNP per 1000 bases. The human genome is about 3 Gbps long and therefore about 3 million SNPs among two random people. With about 20,000 genes each having a coding sequence (exons) about 1.5 kb long (i.e. about 500 amino acids long protein on average), the human coding sequence covers 30 Mbp or about 1 percent of the genome. If SNPs were randomly distributed along the genome that will suggest about 30,000 SNP across the genome coding sequence or just over 1 per gene coding sequence.

g. Humans carry on average one to two mutations that, if inherited from both parents, can cause severe genetic disorders or death before reaching reproductive age. These mutations are what are referred to as recessive alleles of a gene.

h. Mosaicism refers to individuals with genetically distinct cell lines that originated from a single zygote, whereas chimerism refers to those who originated from more than one zygote. Microchimerism  is the co-existence of two genetically different cell populations in one organism, of which one occurs in a very low number.

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