Nucleic Acids

Question 1

How does DNA replication occur?

Answer 1

1. DNA helicase unwinds double strand
2. Creates a Y fork with a leading and lagging strand which act as templates
3. RNA primer binds to leading strand, acting as a point for DNA synthesis. DNA polymerase binds to leading strand and adds dNTPs to the DNA strand.
4. RNA primer also binds to the lagging strand and Okazaki fragments are added to the DNA strand.
5. Exonuclease removes primers
6. Gaps where primer was are filled with nucleotides and proof-read.
7. DNA ligase seals the two strands

Question 2

What is discontinuous DNA replication?

Answer 2

The addition of Okazaki fragments to the lagging DNA strand using an RNA primer.

Question 3

Which is the only achiral amino acid?

Answer 3

Glycine; x2 Hs

Question 4

Where are disulphide bonds added to the protein?

Answer 4

In the ER.

Question 5

What do red blood cells and lymphocytes have in common?

Answer 5

They derive from the same progenitor cell.

Question 6

In a blood smear will you see more lymphocytes or red blood cells?

Answer 6

Red blood cells.

Question 7

Which is the most common chromosome abnormality in humans?

Answer 7

Down’s syndrome: Trisomy 21.

Question 8

The human genome consists of how many base pairs?

Answer 8

6 x 10^9.

Question 9

The human genome is approximately how long?

Answer 9

2m.

Question 10

The human genome has how many autosomal chromosomes?

Answer 10

22 pairs.

Question 11

Which two proteins are required for gene transcription?

Answer 11

RNA polymerases and transcription factors.

Question 12

Which RNA polymerase transcribes mRNA?

Answer 12

RNA polymerase II

Question 13

Which RNA polymerase transcribes tRNA?

Answer 13

RNA polymerase III

Question 14

Which RNA polymerase transcribes rRNA?

Answer 14

RNA polymerase I

Question 15

Where is the initiation point for RNA polymerase II to begin transcription of mRNA?

Answer 15

The TATA box

Question 16

Which is the first transcription factor to bind to the TATA box?

Answer 16

TFIID.

Question 17

Which transcription factor binds to TFIID and RNA polymerase?

Answer 17

TFIIB.

Question 18

Give 2 functions of the Basal transcription complex.

Answer 18

To allow unwinding of the DNA and to allow phosphorylation of RNA polymerase to then begin transcription.

Question 19

What is the basal transcription complex?

Answer 19

A complex made up of RNA polymerase II and transcription factors.

Question 20

What is the building block of chromatin?

Answer 20

The nucleosome

Question 21

Which facilitates transcription - acetylation or deacetylation of DNA?

Answer 21

Acetylated histones.

Question 22

Name 3 things that affect transcription factor expression

Answer 22

Stress, hormones, light, heat, growth factors, voltage.

Question 23

What are the odds of breast cancer in women?

Answer 23

1 in 10.

Question 24

Oestrogen is a steroid hormone. True or false.

Answer 24

True.

Question 25

What is a gene promotor?

Answer 25

A region of DNA that initiates transcription of a particular gene.

Question 26

What is spliced from mRNA? Introns or exons?

Answer 26

Introns; non-coding parts of the DNA.

Question 27

Which virus can interfere with the CAP protein?

Answer 27

Poliomyelitis produces enzymes which remove CAP.

Question 28

Describe the structure of the gene promotor.

Answer 28

Transcription factor binding sites + TATA box.

Question 29

Describe transcription in Escheria Coli

Answer 29

Sigma binds to TATAAT (Pribnow box). Transcription is quicker; bacteria have no nucleus so transcription occurs in same place as translation.

Question 30

What is the primary RNA transcript?

Answer 30

Pre-mRNA (mRNA before splicing).

Question 31

The sequence information contained in the final mRNA

is encoded “discontinuously” in the DNA of the gene. True or false?

Answer 31

True; from pre-mRNA to mRNA there is splicing of introns at irregular points on the strand.

Question 32

Are introns transcribed?

Answer 32

Yes. They are removed in between transcription and translation.

Question 33

Splicing of introns occurs on which strand?

Answer 33

Pre-mRNA (NOT mRNA).

Question 34

Introns begin and end with which sequences?

Answer 34

Begin with: GU and End with: AG.

Question 35

How does the spliceosome recognise introns?

Answer 35

The pre-mRNA carries motifs in its structure which the spliceosome looks out for.

Question 36

Which part of the spliceosome binds to the splice donor site?

Answer 36

U1.

Question 37

Which part of the spliceosome binds to the splice acceptor site?

Answer 37

U5.

Question 38

On which end of the pre-mRNA is the splice donor site?

Answer 38

5’

Question 39

The CAP structure is methylated in its formation at which point?

Answer 39

N7 (nitrogen no. 7 in ring).

Question 40

Name one way to monitor progress of protein translation.

Answer 40

As translation progresses, the A tail becomes shorter.

Question 41

Mutations in Duchenne Muscular Dystrophy are most commonly what type?

Answer 41

Deletions

Question 42

Which antibiotic inhibits initiation in translation?

Answer 42

Streptomycin

Question 43

Which antibiotic inhibits translocation during translation? (movement of tRNA from a site to p site)?

Answer 43

Erythromycin

Question 44

Where does protein synthesis take place?

Answer 44

In the cytoplasm