Transcription

Question 1

Template strand

Answer 1

Strand to which RNA pol makes complementary RNA strand

Question 2

Coding strand

Answer 2

Strand that winds up being essentially the DNA version of the newly synthesized RNA strand
Complementary strand to template strand

Question 3

Promoter

Answer 3

DNA sequences that define where transcription of a gene by RNA polymerase begins

Question 4

+1 site

Answer 4

Site at which RNA pol begins transcription

Question 5

Terminator

Answer 5

Sequence of DNA that marks the end of the gene being transcribed

Question 6

Numbering of gene sites

Answer 6

Negative numbers are upstream of promoter (further in the 5’ direction)
Positive numbers are down stream of terminator (further in the 3’ direction)

Question 7

Overview of transcription

Answer 7

1. DNA is locally denatured
2. RNA pol assembles NTPs complementary to the template strand (no primer needed)
3. RNA-DNA duplex dissociates
4. DNA duplex reanneals

Question 8

Direction of reading of template and of synthesis of RNA strand

Answer 8

RNA pol reads template in 3’ to 5’ direction and synthesizes in the 5’ to 3’ direction

Question 9

Sigma subunit

Answer 9

Part of RNA pol in prokaryotes

Binds to promoter sequence, beginning transcription

Question 10

Initiation of transcription in E. coli

Answer 10

1. Sigma unit binds to 2 consensus (-10 box and -35 box), orienting RNA pol at +1 site
2. RNA pol can start synthesizing RNA (doesn’t require primer)

Question 11

Nascent strand

Answer 11

Growing strand in synthesis

Question 12

Termination of transcription in prokaryotes

Answer 12

Hairpin in mRNA causes RNA pol to stop transcribing

RNA-DNA duplex is dissociated by rho helicase

Question 13

Differences between prokaryote and eukaryote transcription

Answer 13

1. 3 RNA pols in euks; 1 RNA pol in proks
2. RNA processing in euks; none in proks
3. Coupled transcription and translation in proks; no coupling in euks
4. Polycistronic RNA in proks (many genes encoded in same RNA molecule); monocistronic RNA in euks (1 gene/ RNA molecule)

Question 14

RNA pol I

Answer 14

Transcribes rRNA (ribosomal RNA) in euks

Question 15

RNA pol II

Answer 15

Transcribes mRNA (messenger RNA) and snRNA (small nuclear RNA that is non-coding) in nucleoplasm of euks

Question 16

RNA pol III

Answer 16

Transcribes tRNA (transfer RNA) and 1 kind of rRNA in nucleoplasm of euks

Question 17

Initiation of transcription in euks

Answer 17

General transcription factors (GTFs) bind to core promoter, recruiting RNA pol to form preinitiation complex (PIC)

Question 18

Naming of GTFs

Answer 18

GTFs are named according to the polymerase they recruit

Question 19

Elongation in euks

Answer 19

RNA pol II denatures DNA to form transcription bubble
RNA pol II catalyzes NTP addition to the 3’ end of RNA
5’ methyl G cap is added to RNA and introns are spliced

Question 20

5’ methyl G cap

Answer 20

Methylated guanine nucleotide
Added to 5’ end of mRNA
Protects RNA from exonucleases and ensures correct positioning of ribosome during translation

Question 21

Introns

Answer 21

Euk genes only
Long insertions of non-coding sequences
Intervening sequences: transcribed, but not translated
Buffer against mutation and contain enhancer sequences

Question 22

Exons

Answer 22

Sequences that are expressed

Transcribed and translated

Question 23

Termination through polyadenylation

Answer 23

1. mRNA is cleaved at poly A site
2. mRNA is released
3. 50 to 250 adenine nucleotides are added to 3’ end by poly A polymerase

Question 24

Poly A tail

Answer 24

Added to 3’ end of mRNA at end of transcription

Protects mRNA from 3’ to 5’ exonucleases and aids in translation