Molecular Biology (8) Flashcards
What is the structure of normal adult beta-globin primary transcript?
3 exons divided by 2 introns
What is the structure of normal beta-globin mRNA?
3 exons
What is the effect of SNP destroying 3’ splice site?
Exon skipping - one large mRNA transcript made
What is the effect of SNP destroying 3’ splice sites and activating cryptic splice sites?
mRNA has one exon extended
What is the effect of SNP creating new splice sites?
Inserts additional exons
What is the pathological effect of B-globin alternative splicing?
Beta-thalassemia - acute anaemia
How does tissue-specific control work with regards to transcription?
Via promoter - using proximal elements and distal enhancers
How does distal activation of transcription work?
Activator protein binds to enhancer site
DNA bends back over transcription complex
Enhancer with bound activator binds to mediator protein - bound to transcription complex
Upregulates transcription
What is the ffect of chromatin condensation?
Less accessible to enzymes
How do chromatin-remodelling complexes affect the TATA box?
TATA box usually wrapped around histone - inaccessible to TBP
Chromatin-remodelling complexes unwind DNA - allows DNA sliding so TATA box between nucleosomes - TBP can bind
What is the effect of acetylation of nucleosomal histone protein tails?
Weakens electrostatic interactions with DNA - loosens DNA winding - transcribed
What is the process of DNA methylation?
Addition of methyl groups to cytosines of CpG sites on DNA
What are CpG islands?
Areas of DNA sequence with high CpG frequency - mainly transcription start sites in promoter
What is the effect of hypermethylation?
Silences genes
What is the effect of hypomethylation?
Increases gene activity
