Understanding:
7.1.U2: Nucleosomes help to supercoil the DNA Objective:
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Chromosome Structure
In eukaryotic organisms, the DNA is packaged with histone proteins to create a compacted structure called a nucleosome
Organisation of Eukaryotic DNA
In eukaryotic organisms, the DNA is packaged with histone proteins to create a compacted structure called a nucleosome
- Nucleosomes help to supercoil the DNA, resulting in a greatly compacted structure that allows for more efficient storage
- Supercoiling helps to protect the DNA from damage and also allows chromosomes to be mobile during mitosis and meiosis
Organisation of Eukaryotic DNA
- The DNA is complexed with eight histone proteins (an octamer) to form a complex called a nucleosome
- Nucleosomes are linked by an additional histone protein (H1 histone) to form a string of chromatosomes
- These then coil to form a solenoid structure (~6 chromatosomes per turn) which is condensed to form a 30 nm fibre
- These fibres then form loops, which are compressed and folded around a protein scaffold to form chromatin
- Chromatin will then supercoil during cell division to form chromosomes that are visible (when stained) under microscope