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Organisation & Control of Prokaryotic & Eukaryotic Genome by Mind Map: Organisation & Control of
Prokaryotic & Eukaryotic
Genome
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Organisation & Control of Prokaryotic & Eukaryotic Genome

Level of Genetic Code

Increase in number of copies of genes

VIA

Gene Amplification, Repeated firing of multiple DNA replication origins, Unequal chromosomal exchange between 2 non-sister chromatids, Due to: Incorrect synapsing of bivalents, Chromosomal breakage across 2 sister chromatids, Frayed ends which fuse and break apart during anaphase unequally, Slippage during DNA replication leading to folding back of the strand

Transcriptional Level

Change in structure of DNA (packing)

Modification of chromatin structure, DNA methylation, Formation of CpG islands in promoter region, Histone modification, Acetylation, Histone acetyltransferase (HAT), New node, New node, Lysine residues become uncharged, histones dissociate from DNA --> Transcriptionally active, Deacetylation, Histone deacetylase (HDAC), Lysine residues +vely charged again, histones bind to DNA --> Transcriptionally inactive

Control elements

Promoters + TATA box (-20 to -30), Bind general transcription factors

Distal, Enhancers, Bind activators, Increase rate of transcription, Silencers, Bind repressors, Decrease rate of transcription

Combinatorial control of gene expression

Variation in types of numbers of control elements & specific transcription factors

Coordinately controlled genes, Eukaryotic form of 'operon model', Promote simultaneous transcription of certain related genes, Eg. By signal transduction

Post-Transcriptional Level

Pre-mRNA --> Mature mRNA

5' 7-methylguanosine cap

Prevents degradation by RNAses

Recognition of mature mRNA by ribosome

3' poly-A-tail (200 A)

Stabilize mRNA: Length regulates lifespan of mRNA & polypeptide yield

Splicing

Splicing out of introns

Splicing together of exons

Enables alternative splicing of mRNA, One gene/mRNA encodes many different polypeptides

Editing of mature mRNA

Modifying of nucleotide sequence

Translational Level

Half-life of RNA

5' cap + 3' poly-A-tail

5' and 3' UTRs, Varying sequences affect the affinity of mRNA for RNAses

Varying abundance & activity of eIFs

Widespread effect on all translation activity

Activation/Inactivation by phosphorylation/dephosphorylation

Regulatory proteins

Bind at 5' UTR to prevent binding of eIFs & ribosome

RNA silencing

siRNAs (dsRNA), Cleaved by Dicer, Associates with RISC (RNA induced silencing complex), New node

miRNAs (ssRNA), Pair with mRNA, Block translation, Target for degradation

Post Translational Level

Attachment of functional groups (eg. phosphate)

Via enzymes such as kinases

Structural changes to polypeptide (Eg. preproinsulin)

Protein degradation by ubiquitin in proteasome

Eg. cyclins