Unit 2 - Transcription

Question 1

RNA is transcribed from the

Answer 1

5’ to 3’ direction

Question 2

UTR

Answer 2

Un-Translated Region

Question 3

AUG

Answer 3

translation starts

Question 4

Prokaryotic Initiation

Answer 4

Binding of RNApol, Promoter melting, Initial transcription

Question 5

Prokaryotic Elongation

Answer 5

Conformational changes in RNApol, Start of transcription, Unwinding, elongation, & re-annealing

Question 6

Prokaryotic Termination

Answer 6

Use of terminators, Stop & release of the RNA product.

Question 7

Core polymerase

Answer 7

Unit in RNA pol that catalyzes RNA synthesis but cannot initiate elongation unless dissociated from subunit.

Question 8

Sigma subunit

Answer 8

Unit in RNA pol that facilitates polymerase binding to DNA at -35 & -10 promoter elements

Question 9

two important DNA sequences within the promoter in prokaryotes

Answer 9

10 and -35 elements are six nucleotides each, and are located either 10 or 35 base pairs upstream of the actual start site of transcription

Question 10

release of sigma factor

Answer 10

RNA pol can start elongation process

Question 11

The place at which RNA synthesis stops

Answer 11

termination signal, recognized by RNA pol.

Question 12

rho-Independent termination

Answer 12

Utilizes a stem loop & UUUU (intrinsic sequence) on DNA sequence. No protein needed, hairpin (on RNA) disrupts RNApol and transcription is terminated.

Question 13

rho-Dependent termination

Answer 13

requires a stem loop & rho protein. rho protein has an ATP-dependent helicase activity. Rho binds to its rho recognition site, moves along the RNA until it reaches the RNA pol that is paused at the termination site. Then rho will separate the RNA-DNA helix, releasing RNA.

Question 14

Rifampicin

Answer 14

Used in treating tuberculosis (a.k.a., Dactinomycin). Action: Inhibits initiation of transcription by binding to the b subunit of prokaryotic RNA polymerase thus preventing growth.

Question 15

Eukaryotic initiation

Answer 15

requires binding of specialized, general transcription factors and RNApol to promoter sites at the beginning of a gene.

Question 16

Eukaryotic Elongation

Answer 16

requires local unwinding of DNA helix, includes synthesis of RNA transcript.

Question 17

Eukaryotic Termination

Answer 17

not well characterized. Release of newly synthesized transcript

Question 18

Eukaryotic Post-processing

Answer 18

5’ capping, 3’ poly-A tail addition, splicing.

Question 19

RNApol1

Answer 19

transcribes three major rRNAs

Question 20

RNApol2

Answer 20

transcribes mRNA

Question 21

RNApol3

Answer 21

transcribes tRNA (and small rRNA)

Question 22

TFIIs (A, B, D, E, and H)

Answer 22

required by RNApol II

Question 23

TFIID

Answer 23

Binds to the AT-rich promoter element called the TATA box, contains TATA-binding protein (TBP).

Question 24

TATA-binding protein (TBP)

Answer 24

functions much like the bacterial s factor in that it allows the TFIID complex to recognize and bind to the TATA box.

Question 25

TFIIH

Answer 25

a multisubunit protein complex that has two activities: Helicase activity, Kinase activity (phosphorylates the C-terminal domain (CTD) of RNApolII)

Question 26

When CTD is phosphorylated

Answer 26

CTD no longer binds to GTFs and GTFs are released, beginning enlongation.

Question 27

5’ “Capping”

Answer 27

The 5’ end of the pre-mRNA is modified by the addition of a 7-methylguanosine as soon as mRNA synthesis begins. provides stability to the RNA molecule by protecting it from degradation by nucleases. also plays an important role in positioning mRNA on the ribosome for initiation of translation.

Question 28

7-methylguanosine

Answer 28

a guanosine molecule that has been methylated (FYI, at position 7 of the purine ring)

Question 29

Purpose of the poly(A) tail

Answer 29

(i) required for stability of the mRNA; (ii) functions as a signal for export of the mRNA from the nucleus to the cytoplasm; (iii) efficient re-initiation of translation (interacts with 5’cap).

Question 30

protein coding sequences

Answer 30

Exons = “expressed regions”

Question 31

noncoding sequences

Answer 31

Introns = “intervening regions”

Question 32

pre-mRNAs

Answer 32

Not-yet-spliced mRNAs are called “primary transcripts” or pre-mRNAs, and contain both exons and introns.

Question 33

RNA Splicing : 5 Steps

Answer 33

1. Cleavage at 5’ splice site. 2. Folding of intron mRNA into a lariat structure at the branch point. 3. Cleavage at the 3’ end. 4. Assembly of neighboring exons to form mature mRNA.5. Lariat degraded by nucleases.

Question 34

spliceosome

Answer 34

a complex composed of both protein and snRNA that excise introns and ligate (splice) exons.

Question 35

alternative splicing

Answer 35

The use of different patterns of splicing to give rise to different mRNA sequences ( and thus different protein products).

Question 36

always transcribe in the 5’ to 3’ direction

Answer 36

RNA polymerases

Question 37

does not need a primer

Answer 37

RNA polymerase

Question 38

Prokaryotic Transcription Initiation Complex

Answer 38

Holoenzyme

Question 39

Eukaryotic Transcription Initiation Complex

Answer 39

TFIID(TBP), General Transcription Factors, and RNA polymerase II

Question 40

Prokaryotic Start Sequence

Answer 40

35 and 10 promoter sequences

Question 41

Eukaryotic start sequence

Answer 41

(-10) TATA box

Question 42

Prokaryotic post-processing

Answer 42

None

Question 43

Eukaryotic post-processing

Answer 43

5’ 7-methylguanosine cap, Splicing, 3’ poly-A tail