BCMB2901 Lecture Notes - Lecture 4: Histone Octamer, Histone H1, Non-Coding Rna
15 May 2018
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Lecture 4: The eukaryotic genome
How many proteins can be encoded by _____ genome?
• E. coli: ~3,000
• Human: ~30,000
Human genome
• 30,000 protein coding gene sequence constitute 2% of genome
• Regulatory sequences
• Introns (~25% of genome) – *the stuff removed
• Pseudogenes (section of chromosome that is imperfect copy of functional gene)
• Non-coding RNA (e.g. infrastructural RNA, regulatory RNA)
• Repetitive sequences: ~40% of human genome
o e.g. microsatellites & minisatellites
Need for compaction of DNA
• human cell has 6000 million bp of DNA
• each base pair has a thickness of 3.4 A
• total length of DNA ~2m
• typical human nucleus diameter 10-15 μm
Compaction of DNA in eukaryotes
• packaging begins with formation of nucleosome
• DNA wound around small proteins called histones
• Histone have lots of lysine & arginine residues, making them very positively charged at pH 7
Histones
• 5 classes: H1, H2A, H2B, H3, H4
• Core histones: H2A, H2B, H3, H4
o Dimers of each of these together form an
octamer = ‘core’ of nucleosome
• Core DNA = ~147 bp of DNA that wrap around core
histones
• Histone octamer + core DNA = nucleosome
Document Summary
How many proteins can be encoded by _____ genome: e. coli: ~3,000, human: ~30,000. Human genome: 30,000 protein coding gene sequence constitute 2% of genome, regulatory sequences. Introns (~25% of genome) *the stuff removed: pseudogenes (section of chromosome that is imperfect copy of functional gene, non-coding rna (e. g. infrastructural rna, regulatory rna, repetitive sequences: ~40% of human genome, e. g. microsatellites & minisatellites. Need for compaction of dna: human cell has 6000 million bp of dna, each base pair has a thickness of 3. 4 a total length of dna ~2m typical human nucleus diameter 10-15 m. Compaction of dna in eukaryotes: packaging begins with formation of nucleosome, dna wound around small proteins called histones, histone have lots of lysine & arginine residues, making them very positively charged at ph 7. Chromatin: made of nucleosomes, nucleosomes made of dna wrapped around histone cores.
