In: Biology
Mammals contain a diploid genome consisting of at least 10^9 bp. If this amount of DNA is present as chromatin fibers, where each group of 200 bp of DNA is combined with 9 histones into a nucleosome, determine:
a.) the total number of nucelosomes in all fibers
b.) the number of molecules of each type of histone protein associated with the genomic DNA.
Answer
a.)
The total number of nucleosomes in all fibers
= (Total Base Pairs) / (Number of Base Pairs combining with
Histones per Nucleosome)
= 109 / 200
= 5,000,000 nucleosomes in all fibers
Answer
b.)
A nucleosome contains 9 histones, namely:
2 units of H2A histones
2 units of H2B histones
2 units of H3 histones
2 units of H4 histones
1 unit of H1 histone
Hence, the number of molecules of each type of histone protein
associated with the genomic DNA:
5,000,000 nucleosomes in all fibers * 2 units of H2A histones each
= 10,000,000 H2A histones
5,000,000 nucleosomes in all fibers * 2 units of H2B histones each
= 10,000,000 H2B histones
5,000,000 nucleosomes in all fibers * 2 units of H3 histones each =
10,000,000 H3 histones
5,000,000 nucleosomes in all fibers * 2 units of H4 histones each =
10,000,000 H4 histones
5,000,000 nucleosomes in all fibers * 1 unit of H1 histone each =
5,000,000 H1 histones