Molecular biology 3
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Status: S1LectNotes Time: 2025-03-15 Tags: lecturenotes Links:
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epigenetics is how the expression of a gene is modulated without changes to the genetic sequence itself through turning the gene on and off
histone packing is an example of this
heterochromatin is inaccessible for translation
histone tails are positively charges which attracts to the dnas negatively charges
acetylation makes the histone tails neutral, discouraging packing
chromatin is dynamic
posttranslationsal chemical modifications of certain amino acids in the histone tails
acetylation methylation ubiquination phosphorylation
de methylation makes genes more accessible
posttranslational modificaition also affect transcription indirectly though proteins affecting them
chemical modifications can be affected ed by toxins viruses medication diet exercise sleep alcohol stress etc
methylation can also happen directly to the gene promoters
methylate cytosine turns off genes by attaching to methyl binding proteins which can either block or recruits proteins which de acetylates the histones remodeling dna to heterochromatin
highly expressed genes (housekeeping genes) have islands of cgcgcg nucleotides at their promoters for turning on and off
differs from tata box as tata box is mainly for genes need to rapidly be switched on and off
germline genes tend to be “reset” dna methylation can be a source of mutation c → t
chemical modification can lead to all sorts of damage and mutation