A chromatin fibre has a length of 60 nm. If it consist of 30 nucleosom...
Given: Length of chromatin fiber=60 nm
Number of nucleosomes=30
Length of DNA wrapped by nucleosomes =180bp
So,total length of the DNA = 30 × 180 bp = 5400 bp.
If one bp = 0.34nm, length of DNA would be 5400 × 0.34 nm =1836 nm.
Then the degree of compaction of the DNA in the chromatin fibres =
Total length of DNA/ Length of chromatin fibre = 1836nm /60 nm = 30.6
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A chromatin fibre has a length of 60 nm. If it consist of 30 nucleosom...
Explanation:
1. Understanding Chromatin Fibre:
Chromatin is the material present in the nucleus of a cell that consists of DNA, RNA, and proteins. It is a complex structure that undergoes various levels of compaction to fit inside the nucleus. The basic unit of chromatin is the nucleosome.
2. Nucleosome Structure:
A nucleosome is formed by DNA wrapped around a histone protein core. The core consists of eight histone proteins - two copies each of histones H2A, H2B, H3, and H4. The DNA is wrapped around this histone core in approximately 1.65 turns. The DNA wrapped around the histone core is called the nucleosome core particle.
3. Determining the Length of Chromatin Fibre:
Given that the chromatin fibre has a length of 60 nm, we need to calculate the length of DNA in the fibre. Each nucleosome core particle consists of approximately 147 base pairs (bp) of DNA. However, in this case, the DNA wrapped around each nucleosome is 180 bp. Therefore, the length of DNA in each nucleosome is 180 bp.
4. Calculating the Length of DNA in the Chromatin Fibre:
Since there are 30 nucleosomes in the chromatin fibre, we can calculate the total length of DNA as follows:
Length of DNA = Number of nucleosomes × Length of DNA in each nucleosome
Length of DNA = 30 nucleosomes × 180 bp/nucleosome
Length of DNA = 5400 bp
5. Calculating the Degree of Compaction:
To calculate the degree of compaction, we need to compare the length of the DNA in the chromatin fibre to the actual length of DNA if it were fully stretched out. The actual length of DNA is approximately 0.34 nm/bp.
Actual length of DNA = Length of DNA × 0.34 nm/bp
Actual length of DNA = 5400 bp × 0.34 nm/bp
Actual length of DNA = 1836 nm
Degree of compaction = Length of chromatin fibre / Actual length of DNA
Degree of compaction = 60 nm / 1836 nm
Rounding off to one decimal place, the degree of compaction is 30.6.