Chromosome Oragnisation. What chromosome is made of? - chromosome is made of chromatin (nucleic acid...
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Transcript of Chromosome Oragnisation. What chromosome is made of? - chromosome is made of chromatin (nucleic acid...
![Page 1: Chromosome Oragnisation. What chromosome is made of? - chromosome is made of chromatin (nucleic acid and protein). - when in mitotic and meiotic stages.](https://reader035.fdocuments.us/reader035/viewer/2022062519/5697bfc91a28abf838ca8eb4/html5/thumbnails/1.jpg)
ChroChromosome Oragnisation mosome Oragnisation
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What chromosome is made of?What chromosome is made of?
- chromosome is made of chromatin (nucleic acid and protein).
- when in mitotic and meiotic stages of cell cycle, chromatin (euchromatin & heterochromatin) stains readily.
![Page 3: Chromosome Oragnisation. What chromosome is made of? - chromosome is made of chromatin (nucleic acid and protein). - when in mitotic and meiotic stages.](https://reader035.fdocuments.us/reader035/viewer/2022062519/5697bfc91a28abf838ca8eb4/html5/thumbnails/3.jpg)
Chromosome PackagingChromosome Packaging
Chromatin is organised on three basic levels:
- primary (nucloesome)
- secondary (solenoid)
- tertiary/quaternary (final folding into chromosome shape)
A typical eukaryotic chromosome contains 1 to 20 cm of DNA. During metaphase of meiosis/mitosis, this DNA is package into a chromosome with a length of only 1 to 10 m (a condensation of almost 104-fold in length from the naked DNA molecule).
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Chromosome PackagingChromosome Packaging
Base pairing
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Chromosome PackagingChromosome Packaging
double strand
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Chromosome PackagingChromosome Packaging
double helix
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Chromosome PackagingChromosome Packaging
beaded string (beads-on-a-string) – nucleosome structure of chromatin
![Page 9: Chromosome Oragnisation. What chromosome is made of? - chromosome is made of chromatin (nucleic acid and protein). - when in mitotic and meiotic stages.](https://reader035.fdocuments.us/reader035/viewer/2022062519/5697bfc91a28abf838ca8eb4/html5/thumbnails/9.jpg)
Chromosome PackagingChromosome Packaging
nucleosome
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Chromosome PackagingChromosome Packaging
- nucleosome contains histones (2 of each H2A, H2B, H3 and H4, and one H1)
- histones (102 amino acid residues; containing up to 20% lysine and arginine) are highly positively charged – to counteract the negative charges of the phosphate groups on the double helix backbone.
- modification (acetylation, methylation or phosphorylation) of histone tail will affect the level of positive charge to regulate DNA compaction.
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Chromosome PackagingChromosome Packaging
- the diameter of nucleosome (bead) is 11nm.
- 200 bp of DNA associated with one bead, 145 bp are associated with the histone core, 23 bp protected by H1 and 8 to 114bp (depends on species and type of cells) form a linker between beads.
- the rate of DNA winding is 1.7 turns per core particle, producing a six- to sevenfold reduction in the length of DNA.
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Chromosome PackagingChromosome Packaging
Second level of chromatin organization: solenoid
- the nucleosome is supercoiled and organised into a solenoid structure, with 6-7 nucleosomes per turn.
- H1 stabilizes the structure of solenoid.
- the supercoiling produces a fibre of approximately 30nm in diameter.
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Chromosome PackagingChromosome Packaging
Higher order folding of chromatin into chromosome
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What are the roles of chromosome What are the roles of chromosome packaging? packaging?
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Roles of Chromosome PackagingRoles of Chromosome Packaging
Protection
Compaction
DNA metabolism