Molecular medicine

Question 1

Outline transcription?

Answer 1

1) Topoisomerase unwinds DNA supercoils
2) DNA helicase breaks H+ bonds and exposes the nucleotides
3) Single stranded binding proteins stop DNA strands reannealing
4) RNA polymerase binds at TATA promoter region
5) Read 3’ to 5’ direction , form 5’ to 3’
6) Adds one ribonucleotide at a time until stop codon is reached (UAA/UAG/UGA)
7) mRNA strand produced with a poly-A tail and 5’ cap

Question 2

What is start codon?

Answer 2

AUG methionine

Question 3

State stop codon?

Answer 3

UAA
UAG
UGA

Question 4

Function:
topoisomerase
DNA helicase
SSB
RNA polymerase

Answer 4

topoisomerase- unwind DNA supercoil
DNA helicase- break H bond expose nucleotides
SSB- prevent DNA strands reannealing
RNA polymerase- add ribonucleotide

Question 5

Which direction does RNA polymerase read, form?

Answer 5

read- 3’-5’
form- 5’ to 3’

Question 6

What are introns?

Answer 6

Non-coding

Question 7

Explain splicing?

Answer 7

1) Removal of introns (non-coding segments) to form fully coding strand
2) Carried out in nucleus by slicosomes
3) Exons spliced back together
4) Mature mRNA leaves nucleus via nuclear pores

Question 8

Where does splicing occur? By what?

Answer 8

Nucleus- slicosomes

Question 9

How does mature mRNA leave nucleus?

Answer 9

Nuclear pores

Question 10

Explain translation?

Answer 10

1) mRNA binds to ribosome which has small and large subunits
2) tRNA carries anticodons
3) tRNA binds to ribosome
4) mRNA moves in a 3’ to 5’ direction and the anticodon binds to mRNA
5) As each amino acid bound- mRNA shifts along ribosome
6) Termination codon- ribosome detaches and mRNA is broken down in the cytosol

Question 11

What comes first transcription or translation?

Answer 11

Transcription- 1st stage
Translation- 2nd stage

Question 12

What are 3 main types RNA?

Answer 12

messenger RNA (mRNA)
transfer RNA (tRNA)
ribosomal RNA (rRNA)

Question 13

What are 3 stop codons?

Answer 13

1) UAA
2) UAG
3) UGA

Question 14

Define single nucleotide polymorphism? (SNP)
Example?

Answer 14

Single nucleotide differs

Sickle cell
CF

Question 15

What subunits in haemoglobin?

Answer 15

2 alpha and 2 beta

Normal adult- HbA
Sickle cell- HbS

Question 16

What is SNP in sickle cell?

Answer 16

GAG to GTG- 17th nucleotide

Question 17

Is sickle cell autosomal recessive or dominant?
Both parents- chance?
SNP?

Answer 17

Autosomal recessive
1 in 4, 50% carrier
GAG to GTG in 17th nucleotide

Question 18

What functional change in sickle cell?

Answer 18

1) Cells don’t live as long
2) Lower affinity for oxygen
3) Stuck in blood vessels
Reduced delivery of O2 to muscles

Question 19

State diff protein structure?

Answer 19

1o - linear chain of amino acids- covalent bonds
2o = alpha helix, beta pleated sheets- H+ bonds
3o = 3D structure of a single chain of amino acids
VdW, H+ bonds, Electrostatic, Ionic, Disulphide bridges
4o = overall 3D structure of a polypeptide- interaction chains