Gene organisation and transcription – II Flashcards Preview

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What is the role of the Transcription Factor Binding Sites

Control the rate of transcription via transcription factor binding


What is meant by RNA processing?

The initial RNA produced from a gene is known as a “primary transcript” or “Pre- mRNA” or “heterogenous nuclear RNA” ( hn RNA) This primary transcript needs to be processed before it can be used as messenger RNA (mRNA) for protein translation. add pic


Where does RNA processing occur



What are exons?

Segments of the gene which contain sequences that form part of the final RNA are called “exons”


What are Introns?

Introns” are sequences in the gene which are transcribed but are edited out of the final mRNA


What does sequence does an intron start with and end with?

Introns start with the sequence “GU” and end with the sequence “AG”


What is the splice donor site

a donor site which is in the 5' end of the intron where U1 binds


What is the splice acceptor site

acceptor site (3' end of the intron) Where U5 binds


Lable the diagram below add pic

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What are U1 U4 U6 U2 and U5?

small Ribonuclear Proteins, or snRNP’s.


Where does U1 bind?

Splice Donor Site


Where does U5 bind?

Splice acceptor site


Draw a splicesome

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How is the intron removed

Formation of a lariet structure The “branch” results from a phosphodiester bond between the 5’ phosphate on the “G” at the start of the cleaved intron and the 2’ OH of the branchpoint “A”. The phosphodiester bond between the “G” at the end of the intron and the next exon is then cleaved and the intron removed as a “lariat” structure add pic


What is the order the snRNPs bind?

U1 U2,U4,U6 U5


What happens to the exposed adjacent exon sequences?

They get ligated together


Why is the 5' CAP added to pre-MRNA and a Poly A tail in the 3' end

The cap acts to protect mRNA at the 5’ end and also greatly enhances the translation of mRNA. On mRNAs, the poly(A) tail protects the mRNA molecule from enzymatic degradation in the cytoplasm


What is polyadenylation?

Polyadenylation is the addition of a poly A tail to the pre-mRNA