Transcription

Question 0

How is the 5 cap constructed

Answer 0

7 methyl guanosine attached via 5-5 triphosphate bond

Question 1

Example of epigenetic modification

Answer 1

1. DNA methylation- methylated promoter turns off transcription
2. Histone modification- acetyl groups added to histone decrease overall positive charge and because DNA is - charged fosters dissociation with histone complex

Question 2

What are types of mRNA post transcription modification?

Answer 2

5 cap, 3 poly A tail, splicing, methylation of 2’ OH of 1st and 2nd nucleotide in transcription

Question 3

What is the fn of the poly A tail?

Answer 3

stabilize mRNA, facilitates exit from nucleus, aid in translation, shortened in cystol

Question 4

How does splicing occur?

Answer 4

2 transesterification rxns
snRP U1 binds to 5’ GU splice site; U2 binds to branch site; U4 and U6 associate, U5 brings exons 1 and 2 closer
A binding site esterification rxn with GU recognition site on first exon, creates a 2-5 phosphodiester bond on the intron (lariat) and then the OH on the first spliced exon attacks the AG site on the second exon (esterification rxn 2)

Question 5

RNA pol I

Answer 5

makes rRNA upstream promoter

Question 6

RNA pol II

Answer 6

mRNA, TATA box (upstream) or downstream promoter

Question 7

RNA pol III

Answer 7

5s RNA and tRNA

Internal promoter- promotor in transcribed section of the gene