Lecture 12 : Gene Expression
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Housekeeping genes, Specialised proteins
Notes about genes
• Not all genes expressed at same rate, can be abundant or scarce • Genes can either be constitutively expressed (always on), or conditionally expressed (always off) • Most cells express 10000-15000 genes
What is the predominant level of gene control
Translation
Transcriptional control
mRNA population regulated by : - Which genes are transcribed - Rate of transcription - Transcriptional start site used
Regulating gene expression by RNA processing
• Splicing (removing introns) • Capping (addition of 5’methyl cap) • Polyadenylation (Adding 3’poly(a) tail
What is Poll II
• Site of capping • Site of splicing • Site of adding poly(A) tails • Splicesome complex
Why do we have introns
• Important in molecular evolution (exon shuffling) • Allow for alternative mRNA splicing
Splicesome
• snRNPs are large ribonucleoprotein complexes containing ribosomes • Site of splicing • SRSFs can inhibit splicing Shits spliced for a reason
