Transcription

Question 0

DNA always occurs as a ______ while RNA is _______, although RNA can fold into different shapes.

Answer 0

DNA-Double Helix

RNA- single stranded

Question 1

RNA chemically differs from DNA in the fact that …..

Answer 1

RNA contains the sugar ribose (x=OH) instead of deoxyribose (x=H) and the base uracil (U) instead of thymine (base pairing with adenine)

Question 2

DNA Coding Strand 5’- A T G C C A - 3’
DNA Template Strand 3’- T A C G G T - 5’
mRNA 5’- A U G C C A -3’
Protein N- Met- Pro - C

Answer 2

SUPER IMPORTANT.

Note similarity between coding strand and mRNA plus the one difference (TU)

Question 3

Prokaryotic mRNA versus eukaryotic mRNA (structurally)

Answer 3

P- multiple proteins from one mRNA

E- 5’cap, PolyA tail, one protein after splicing.

Question 4

Transcription differs from replication…

• RNA does not remain H-bonded to DNA template but is displaced and the DNA helix reforms
• RNA is ____than DNA

Answer 4

shorter

Question 5

The main enzymes in transcription are ______, similar to DNA polymerases, moving in the _____ direction to create an RNA chain in the _____ orientation

Answer 5

RNA polymerase; moves 3’ to 5’, creates 5’ to 3’

** ALSO employs hydrolysis of high-energy bonds to drive reaction AQ

Question 6

Unlike DNA poly, RNA poly CAN start…

Answer 6

start transcription/growing without a primer

Question 7

The non-template strand is called the ______ strand and is similar in sequence to the RNA transcript with the exception of TU

Answer 7

CODING strand

Question 8

RNA poly recognizes startpoints for transcription and is sensitive to signals to increase or decrease production of gene product dependent on need.

Answer 8

Interesting.

Question 9

A regulatory protein sequence called the _______ is upstream(5’) of start site and controls….

Answer 9

Promoter: controls binding of RNA poly to DNA

Question 10

Frequency of transcription is controlled by _____ within the promoter

Answer 10

cis regulatory sequences

Question 11

RNA poly has a ____ subunit that recognizes promoter DNA sequences that determine the start point and frequency of transcription

Answer 11

sigma

Question 12

Eukaryotes have 3 RNA polys
I–>
II–>
III–>

Answer 12

I–> produces rRNA
II–> produces mRNA
III–> produces small RNAs such as tRNAs and 5S rRNA

Question 13

In E. Coli, the ______sequence is in the promoter and helps mediate poly binding

Answer 13

TATA box/ Pribnow box

Question 14

Elongation continues until RNA poly encounters termination signals such as _____ or ______

Answer 14

Hairpin loop or Rho protein

Question 15

A cistron is a….

Answer 15

region of DNA that encodes for a single polypeptide chain

***just prokaryotes?

Question 16

Prokaryotic transcript products are not modified or spliced like eukaryotes.

Answer 16

Answer.

Question 17

A polycistronic transcript is capable of…

Answer 17

making a number of different proteins from one mRNA

Question 18

BASIC transcription cycle (prokaryotic)
1)
2)
3)

Answer 18

1) Initiation:sigma subunit of RNA poly binds promoter sequence of DNA
2) elongation: 5’ to 3’ polymerization
3) termination: (sigma falls off )RNA forms hairpin or else runs into Rho protein

Question 19

-
-

Answer 19

• Addition of 5’ cap in leader sequence
• splicing out introns (non coding)
• addition of Poly-A tail in 3’ trailer sequence

Question 20

Prokaryotic RNA poly requires ______ but Eukaryotic RNA poly requires…….

Answer 20

P- sigma

E- lots of proteins

Question 21

What complicates eukaryotic transcription?

Answer 21

nucleosomes

Question 22

In eukaryotes, _____ relieve tension while in prokaryotes _______ does so

Answer 22

E- topoisomerases

P- gyrase

Question 23

Capping of mRNA occurs at ____ end and is necessary to …..

Answer 23

5’ end

Protects transcript form degradation and is necessary to be recognized by small ribosomal subunit for translation

Question 24

A complex structure known as ______ ensure that exons are accurately spliced; small ribonucleoproteins called _____ are involved in spliceosome formation

Answer 24

spliceosomes; snRNPs

Question 25

Only the ____ at the start of an intron and the ____ at its end are considered INVARIANT nucleoties

Answer 25

GU; AG

AG is also at end of exon?(3’)

Question 26

1-Adenine in intron attacks 5’ splice site (AG)and cuts backbone of RNA
2-the cut 5’ of intron (GU) covalently attaches to self at original A= loop
3-released 3’- OH end of exon (AG) reacts with start of next exon joining two exons together
4- exon (lariat) is released

Answer 26

THIS IS Slicing.

Question 27

RNA splicing is performed by the _____

Answer 27

spliceosome

Question 28

______splicing is a common means to regulate gene expression

Answer 28

Alternative splicing

Question 29

Two types of slicing errors:

Answer 29

1) exon skipping (exon 1 + exon 3, forgetting exon 2)

2) cryptic splice site selection: not the AG,GU signal

Question 30

Poly-A tail is created at the _____ end of the mRNA. A _______ signals cleavage site for polymerase to numerous Adenines to…

Answer 30

3’ end. polyadenylation sequence

-this slide was confusing

Question 31

microRNAS are involved in ……

Answer 31

regulation of gene expression

Question 32

HIV has the enzyme ______ that produces….

Answer 32

reverse transcriptase that produces dsDNA from viral RNA and then incorporates dsDNA into host genome for expression

Question 33

common antibiotic drugs target bacterial _____

Answer 33

RNA polymerase