Transcription,translation, DNA, RNA

Question 1

What does helicase and unwinding proteins do?

Answer 1

Keep strand separate

Question 2

Differences between DNA,mRNA and tRNA
  Stranding?
  Size?
  Shape?
  Pentode sugar?
  Bases?
  Made and found?
  Proportions in body?
  Chemical stability?

Answer 2

Double,single,single 
Biggest,middle,smallest
Double helix,single helix,clover 
Deoxyribose,ribose,ribose 
ATCG,AUCG,AUCG
Nucleus, nucleus and throughout cell, nucleus and throughout cell
Constant for all cells,varies with metabolic energy,varies with metabolic energy 
V stable, least stable, middle stability

Question 3

What is siRNA?
What does it do?
Sequence?(3)

Answer 3

Small interfering RNA
Breaks down mRNA before its genetic code can be translated

Double stranded mRNA cut with enzyme to smaller sections to produce several siRNA strands
One strands guides enzyme to mRNA strand and attaches to complimentary base pair
Enzyme cuts mRNA which prevents full polypeptide being synthesised

Question 4

Translation

Sequence of events?

Answer 4

Ribosome attaches to starting codon on mRNA
tRNA with complimentary anticodon moves to ribosome and bunds with mRNA
carries aa
Enzyme with ATP binds aa of tRNA with peptide bonds
tRNA released free to collect another aa
Continues until polypeptide is complete and ribosome reaches stop codon

Question 5

Transcription
What’s the sequence of events?
How does this produce many polypeptides?

Answer 5

Length of DNA codes for a cistron
DNA polymerase,helicase and unwinding proteins join at promoter region
Helicase breaks H bonds of double helix
Exposes bases on one side of the DNA molecule
Free nucleotides in nucleoplasm form complimentary base pairs AUCG
RNA polymerase condenses the bases to form new strand of DNA
DNA recoils behind it
Once terminator region reached no longer copied
my mRNA and DNA duplex is unstable so separate allowing mRNA synthesis to start
length of mRNA leaves the nucleus through a nuclear pore and diffuses to ribosomes

Many ribosomes can do this at once
One gene can produce many mRNA and they can be translated to many polypeptides

Question 6

Where are proteins for expert synthesised?
What are they then passed to?
What happens to them there?
And they are eventually?

Answer 6

RER
Golgi app, processed and packaged into vesicles
Passed from cell

Question 7

What are the 3 post transcriptional modifications?

What is methionine?

Answer 7

Removal of methionine
Addition of functional groups eg phosphate
Structural changes eg change in bonding

The starting codon

Question 8

tRNA
  Size?
  What does it have within molecule?
  Why structure ford it have?
  What two regions does it have?
  What is the anticodon region?
  What is required to form high energy bond at aa binding site?

Answer 8

Small
Secondary and tertiary bonding 
3d structure 
Anticodon region and aa binding site 
3 complimentary base pairs 
Condensing enzyme and ATP

Question 9

What does ribosome do to the mRNA?
What are the two areas in the complex?
What is each section associated with?
What sequence of bases is methionine? Where is it aligned?

Answer 9

Hold between two units
P and A
A different mRNA codon
AUG aligned at P site

Question 10

Transcription Factors 
 What are they?
 What does it have that stimulates the process?
 What can't happen without?
 What is it switched off by?
 What can switch it on? Example?
 What does the oestrogen?

Answer 10

Regulatory proteins which initiate transcription
Sites that bind with DNA stimulating process
Transcription
Inhibiting factor
Hormones oestrogen
Oestrogen lipid sol diffuses across memb
Binds to transcriptional factor changing shape so that inhibiting factor is released
Transcriptional factor can now bind to DNA

Question 11

Splicosome
What does it splice to give what?
What is mRNA called before it is spliced?
What is left over after splicing?
Why can a single section of DNA code for up to a dozen proteins?

Answer 11

Introns to give functional proteins
Pre-mRNA
Exons
After splicing exons can rejoin in different combinations