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Lec 7
Transcriptionin Eukaryotes
27
Biology
Undergraduate 2
12/05/2013

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Term
What is miRNA?
Definition
- micro RNA
- 22-24 nucleotides
- controls gene expression
Term
What is snRNA?
Definition
- small nuclear RNA
- needed for mRNA maturation
- part of the spliceosome
Term
What is the function of hnRNA?
Definition
- heterogeneous nuclear RNA
- intermediate form of mRNA (
- the "pre-mRNA" processed to make mRNA
Term
How many RNA Polymerases are there in eukaryotes?
Definition
3
Term
What are the names of all the polymerases in eukaryotes and what do they do?
Definition
Pol 1: transcribes rRNA genes (5.8S, 18S, and 28S)
Pol 2: transcribes mRNA genes
Pol 3: transcribes tRNA genes and the 5S rRNA gene
Term
What is needed for mRNA initiation?
Definition
The formation of a basal transcription initiation complex (several TFIIs) which bind at the TATA box
Term
What facilitates the formation of the basal transcription initiation complex?
Definition
The binding of proximal promoter elements and enhancer elements
Term
How is mRNA modified?
Definition
- by the enzymatic, cotranslational addition of a 7-methyl-G cap and a poly-A tail
Term
What is polyadenylation signal?
Definition
AAUAA, the poly-A tail is added downstream of this
Term
What is added right after the polyadenylation signal?
Definition
~200 AMPs by poly(A) polymerase
Term
What two things help protect mRNA from degradation and facilitate mRNA translation?
Definition
The addition of the 7MG cap, and the poly-A tail
Term
In the event that mRNA is edited after synthesis, name what happens, and two ways it can be done?
Definition
The insertion or deletion of specific nucleotides using:
1) a guide RNA (trypanosome mitochondria)
2) base modification (C-U editing)
Term
True or False: All mRNA gets edited
Definition
False, it is very rare
Term
How are tRNA precursors processed in yeast?
Definition
by endonucleolytic cleavage and ligation
Term
How are Tetrahymena mRNA precursors processed?
Definition
Autocatalytic splicing
Term
How are intervening sequences removed in Tetrahymena?
Definition
Cutting and rejoining by and RNA-catalyzed mechanism
Term
How are introns removed from mRNA precursors in eukaryotes and prokaryotes?
Definition
Sliceosome mediated splicing
Term
What happens after introns are removed?
Definition
Exons are spliced together
Term
What is the result of splicing together exons?
Definition
a mature mRNA transcript
Term
What are spliceosomes composed of?
Definition
5 small nuclear snRNPs
Term
What is contained in an snRNP?
Definition
A specific snRNA (U1, U2, U3, U4, U5, U6)
Term
What do each of the following specific snRNPs recognize? U1, U2, U5
Definition
U1 - the 5' splice site
U2 - branch point A residue
U5 - recognizes the 3' slice site
Term
How is a lariat structure produced?
Definition
Cleavage at the 5' splice site, and joining the intron end to the branch point
Term
What happens after the lariat structure is produced?
Definition
It is removed by cleavage at the 3' splice site
Term
What is the final step of RNA splicing?
Definition
Joining the 5' exon to the 3' exon
Term
How can the coding potential of a gene be increased?
Definition
Differential splicing
Term
What would a mutation affecting a splice site recognition sequences cause?
Definition
Genetic Diseases
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