Transcription and translation

Question 1

Give 5 types or RNA

Answer 1

transfer
messenger 
non coding 
micro 
ribosomal

Question 2

What is the direction of transcription

Answer 2

5’prime to 3’ prime

Question 3

describe initiation, elongation and termination of transcription

Answer 3

initiation is when the promoter sequence is recognised, the transcription initiation factors and RNA polymerase

Elongation - 5’ to 3’ chain growth

termination - sequence dependent

Question 4

the key points of initiation

Answer 4

transcription factors bind to DA and recognise the specific sequence and determines the direction fo transcription.

the transcription factors recruit RNA polymerase and indicates where transcription will start.

Question 5

what are the promoter sequences in eukaryotes

Answer 5

promoter sequences control binding of RNA polmerase to DNA and identifies the start point

e.g. TATA box

there are a variety of upstream sequences which are used in regulation

Question 6

which direction does transcription occur?

Answer 6

always 5’ to 3’

Question 7

key points of elongation

Answer 7

DNA unzips

and mRNA produced

Question 8

describe the coding and template strand

Answer 8

the coding strand is identical to the mRNA (except T and U)

the template strand is complementary and antiparallel to the coding strand

Question 9

give three examples of RNA processing

Answer 9

capping - at the 5’ end : 5’ cap which protects against degradation

Tailing or polyadenylation
a poly A tail at the 3’ end also protects against degradation

splicing
removes introns and is sequence dependent

if a mutation results in intron skipping the resultant mRNA can be very unstable

Question 10

give the three key points for translation

enzyme
activated substrate
template

Answer 10

enzyme: ribosome

activated substrate: amino acids

template mRNA

Question 11

differences in ribosomes of prokayotes and eukaryotes

Answer 11

prokaryotes
3 rRNAs and 56 proteins
30s and 50s subunits = 70s ribosome

Eukaryotes
4 rRNAs and 82 proteins
40s and 60s subunits
= 80s ribosome

important for antibiotic use

Question 12

contrast rRNA, mRNA and tRNA

Answer 12

rRNA
few kinds - many copies of each

mRNA
many different kinds - few copies of each

tRNA
around 100 kinds and very many copies of each

Question 13

give the key features of the genetic code

Answer 13

triplet
non overlapping
degenerate

initiation code AUG
termination UAA, UGA, UAG

Question 14

what are the key components for making mRNA in transcription

Answer 14

enzyme: RNA polymerase
activate substrates: NTPs
template: DNA
in a three stage process: initiation, elongation and termination.