T2 Modules 1+2

Question 1

central dogma of biology

Answer 1

DNA -> mRNA -> protein

where RNA is split into functional RNA (t and r) and mRNA

Question 2

transcription in prokaryotes

Answer 2

3 steps

1) INITIATION
RNAP attaching
- RNA polymerase attaches to promoter region (TATAAT) of DNA via SIGMA FACTOR pr- (diff for diff genes) that binds directly to DNA
- DNA opens, template strand threaded into RNAP
- SF + RNAP = WHOLO enzyme
- transcription then happens in TRANSCRIPTION BUBBLE

2) ELONGATION
nucleotides attaching
- HB between strands
- PDE bond between phosphate and OH group

3) TERMINATION
2 ways to stop transcription
RHO-INDEPENDANT
- inverted repeated sequences
- fold to make GC RICH HAIRPIN LOOP

RHO-DEPENDANT
- RHO FACTOR pr-
- uses ATP, unwinds transcript from DNA

*TRANSCRIPTION + TRANSLATION ARE COUPLED i.e. can happen @ same time
- happens bc no compartmentalization

Question 3

difference between prokaryote and eukaryote transcription

Question 4

what direction is RNA synthesized in? What direction does RNAP move along DNA?

Answer 4

RNA synthesized 5’-3’
RNAP moves 3’-5’ along DNA

Question 5

transcription in eukaryotes

Answer 5

4 steps

1) INITIATION
- general TRANSCRIPTION FACTORS needed to bind RNAP to DNA
3 types of RNAP
1: rRNA
3: tRNA
2: mRNA

2) ELONGATION

3) POST TRANSCRIPTIONAL MODIFICATIONS
5’ cap
- triphosphate link connects 7methylguanosine
- for stability, protection, helps attach ribosome for translation
3’ poly A tail
- POLYADENILATION: 510-200 adenines added after signal sequence AATAAA
RNA SPLICING get rid of unnecessary code

4) TERMINATION
depends on type of RNAP
1: eukaryotic termination factors (similar to rho dep.)
2: poly-A dependant: polyadenilation
3: termination sequence (similar to rho-ind.)

Question 6

name stop and start codons

Answer 6

start: AUG
stop: UAA, UAG, UGA

Question 7

what is the RNA tie club

Answer 7

George Gamow

named 20 amino acids + 4 nucelotides

Question 8

redundancy in AA code

Answer 8

61/64 triplets able to code for AAs

Question 9

explain what a reading frame is

Answer 9

• region of coding strand that can be read for genes
• can be identified via stop and start codons

3 ways to read depending on the nucleotide you start on
1st RF
2nd RF
3rd RF

if nothing known about DNA, either template or coding strand could be read, making 6 POSSIBLE READING FRAMES

Question 10

how to prove that codons come in triplets

Answer 10

adding 1 nucleotide changes succeeding codons

Question 11

frameshift mutation

Answer 11

when the reading frame ‘shifts’ because of nucleotide addition/deletion

when 3 are added/removed, most codons are conserved

Question 12

RNA world hypothesis

Answer 12

• some type of ancestral RNA was the precursor to life.
• probable because RNA plays such a large role in converting genetic info, but theory needs more evidence