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Organisation & Control of Genome

Revision for Organisation & Control of Prokaryotic & Eukaryotic Genome

Elaine P

on 2 August 2016

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Transcript of Organisation & Control of Genome

(i) Structure & organisation of prokaryotic & eukaryotic genome
Size / Packing / Linearity / Introns/ Regulatory Sequences

(ii) Structure & function of non-coding sequences
Intron / Centromere / Telomere / Promoter / Enhancer / Silencer

(iii) Role of telomeres & centromeres
Pg 9, 10
LO - Organisation
(iv) Process & significance of gene amplification
ribosomes in early cell development
(v) Post transcriptional control
Splicing / Polyadenylation / 5' Capping
(vi) Transcriptional control
Control elements (promoter, silencer, enhancers)
Other factors (TFs, repressors, histone modification, DNA methylation)
(vii) Translational control
half-life of RNA / 5' capping / initiation
Post-translation control
biochemical modification / protein degradation
LO - Control
1. Chromatin Remodelling
Histone acetylation -> more diffused structure -> TFs has easier access -> + transcription initiation

2. DNA Methylation
Methylated cytosine residues -> turn off genes -> long term inactivation -> - transcription
DNA level
(availabilty of genes for transcription)
1. Control elements

(a) Proximal control elements
TATA box -> start point
CAAT box & GC-rich sequences -> frequency
(b) Distal control elements
Enhancers +
Silencer -

2. Transcription factors

(a) General TFs (binds proximal control elements)
(b) Specific TFs (binds distal control elements)
Activators +
Repressors -

* Protein mediated DNA bending (Pg 18)
Transcriptional Control
(initiation of transcription)
1. Alteration of mRNA ends
(a) 5' capping +
(b) 3' polyadenylation +

2. RNA Splicing
Introns cut out, exons joined together

*Mechanism & significance of splicing (Pg22)
Post-transcriptional Control
(processing of pre-mRNA)
1. mRNA stability
(a) Length of poly(A) tail
shortened by exonucleases -> trigger removal of 5' cap -> degradation -
(b) destabilising sequences
AU-rich elements in 3' UTR -> short half-life -
(c) IRE at 3' UTR
IRP binds IRE -> enhance stability of mRNA +

2. Initiation
(a) IRE at 5' UTR
IRP binds IRE -
(b) 5' cap & 3' poly(A) tail
enzyme adds more adenine nucleotide -> ribosomal binding
(c) activation / inactivation of eIFs
(global control)
Translational Control
1. Biochemical modification
(a) polypeptide cleavage
(b) chemical modification (phosphorylation / glycosylation)
(c) Transport to target site

2. Protein degradation
Ubiquitin marks protein -> recruit proteosomes -> degradation
Post Translational
1. Early embryonic development
extrachromosomal copies of ribosomal RNA genes -> replicate by rolling-circle mechanism
Gene Amplification
(increase number of DNA tempates)
Full transcript