Molecular Biology

Question 1

How does RNA polymerase add on RNA

Answer 1

Builds new RNA strand in 5’ - 3’ direction.

Can only add RNA nucleotides to the 3’ end of strand.

Question 2

How must the template strand be oriented?

Answer 2

3’-5’

Question 3

Will a polypeptide be made when transcribing the bottom strand ? Problem ?

Answer 3

No it wont, there is no start codon

Question 4

PCR

Answer 4

Polymerase chain reaction. A specific DNA section is replicated over and over by DNA polymerase to amplify the # of copies in that sequence

Question 5

Describe general steps you would take to determine which protein is produced by the particular DNA-sequence

Answer 5

Cut the DNA using restriction enzymes - insert in plasmids, which introduces the bacteria - chem signal will tell the to produce target protein once produced - protein is purified and separated.

Question 6

What colour are the phosphorus atoms on DNA model

Answer 6

Purple

Only colour with 4 other oxygens attached

Question 7

What colour is nitrogen

Answer 7

Blue

Bonded to H’s to form the “rungs in ladder” or nitrogenous bases

Question 8

What colour is oxygen

Answer 8

Red

4 oxygens are used to bind to phosphorus connecting the sugar/phosphate backbone

Question 9

What colour is Hydrogen

Answer 9

White

Connecting the two backbones in the center

Question 10

What colour is carbon

Answer 10

Black

Used to form the ring of deoxyribose sugar - contains 5 carbons

Question 11

Transcribe:

GCT GAC TAG TAC GAT CGT TCG ACT CTT CGG ATT

Answer 11

CGA CUG AUC AUG CUA GCA AGC UGA GAA GCC UAA

Question 12

Steps of transcription

Answer 12

*happens in nucleus
A) INITIATION: promoter DNA determines where transcription begins - begins at +1 site
-Sigma helps initiate by binding to promoter region
-downstream DNA is transcribed 5’-3’
-RNA polymerase unwinds DNA
B) ELONGATION: NTP enters RNA polymerase - mRNA elongates — sigma protein in released once initiation is complete
C) TERMINATION: RNA polymerase transcribes transcription-termination signal on DNA
- in prokaryotes: hairpin loop is formed = physical separation

Question 13

Describe mRNA processing

Answer 13

EXONS: coding segments (stay)
INTRONS: non coding (removed)
SPLICING:
1. SnRNPs bind to adenine at the end of intron
2. SnRNPs join o get her = SPLICEOSOME
3. intron cut on one end - forms loop
4. Other end is cut, exons fill gap - introns are cut out

First 20-40 nucleotides - RNA is capped off with modified form of guanine = 5’ cap
3’ is modified - polypeptides form poly-A tail

Question 14

Describe Translation

Answer 14

3 binding sites - A, P, E

1. INITIATION: small subunit scans mRNA 5’-3’; finds start codon + unites with large subunit
2. ELONGATION: tRNA moves through APE sites and codes while forming polypeptide bonds to make protein
3. TERMINATION: stop signal causes addition of WATER instead of aa - breaks bond between protein chain and tRNA in P Site

-mRNA becomes building blocks again - hydrolysis of GTP molecules is required for separation

Question 15

Compare and contrast purine and pyrimidine bases

Answer 15

Purine:

• Double ring
• adenine + thymine

Pyrimidine:

• Single ring
• cytosine + guanine