2.7 DNA -> Protein

Question 1

Why do we say DNA replication is semi-conservative?

Answer 1

One strand is from the original molecule and one is newly synthesised

Question 2

Which enzymes are involved in the replication of DNA?

Answer 2

Helicase

DNA Polymerase

Question 3

Who confirmed DNA replication was semi conservative and when?

Answer 3

Meselson-Stahl in 1958

Question 4

Describe what a dispersive model of DNA would have meant?

Answer 4

New molecules were thought to be made of segments of old and new DNA

Question 5

Describe what a conservative model of DNA would have meant?

Answer 5

An entirely new molecules is synthesised from an (unaltered) DNA template

Question 6

How did Meselson and Stahl prove that DNA replication was semi-conservative?

Answer 6

DNA was prepared in heavy 15 N (nitrogen) and then allowed to replicate once in 14 N
After 1 replication they were found to contain a mix of 14 and 15 N and after 2 replications some showed only 14N or only 15 N

Question 7

What disproved the conservative model?

Answer 7

That after 1 replication in N14, the DNA molecules contained a mix of N14 and N15

Question 8

What disproved the dispersive model?

Answer 8

That after 2 replications in N14, some DNA molecules were only N14

Question 9

What is the function of helicase?

Answer 9

Unwinds the double helix by breaking hydrogen bonds

Question 10

What is the function of DNA polymerase?

Answer 10

Synthesises new strands by aligning complementary base partners

Question 11

Where does the energy come from for DNA polymerase to add the bases?

Answer 11

The nucleotides are in triphosphate groups, the 2 extra phosphates are released, releasing energy to make link the nucleotide to the new strand

Question 12

What does PCR stand for?

Answer 12

Polymerase Chain Reaction

Question 13

What is the purpose of the PCR technique?

Answer 13

To amplify quantities of a specific sequence of DNA from an initial minute sample

Question 14

By what scale factor does the amount of DNA in a PCR replicate in every cycle?

Answer 14

It doubles

Question 15

Describe the steps of PCR

Answer 15

Denaturation
Annealing
Elongation

Question 16

Describe the step of denaturation in PCR

Answer 16

DNA sample is heated to 90* to separate 2 strands

Question 17

Describe the step of annealing in PCR

Answer 17

Sample is cooled (55*) to allow primers to anneal

Question 18

Describe the step of elongation in PCR

Answer 18

Sample is heated to the optimal temperate for a heat-tolerant polymerase (Taq) to function (75*)

Question 19

What is Taq polymerase

Answer 19

An enzyme used in PCR to extend the nucleotide chain from the primers so that they can be copied

Question 20

What is the optimum temperature of taq polymerase?

Answer 20

75* C

Question 21

Describe transcription

Answer 21

The process by which an RNA sequence is produced from a DNA template

Question 22

Function of RNA polymerase

Answer 22

Separates the DNA strands and synthesises a complementary RNA copy from on of the strand

Question 23

Why do the nucleotides involved in transcription have additional phosphate groups (ribonucleotide triphosphates)?

Answer 23

So that RNA polymerase can remove these phosphates to release the energy needed to covalently bond the nucleotides to the growing sequence

Question 24

What is the direction of transcription?

Answer 24

5’ - 3’

Question 25

What do we call the strand that is transcribed?

Answer 25

The antisense strand

Question 26

What do we call the strand that is not transcribed?

Answer 26

The sense strand

Question 27

Which strand is the RNA produced by transcription identical to?

Answer 27

The sense strand except the Thymine there is Uracil on RNA strands

Question 28

Where does transcription occur?

Answer 28

The nucleus

Question 29

Where does RNA go after transcription?

Answer 29

Cytoplasm (for translation)

Question 30

What does it mean that the genetic code is universal?

Answer 30

Almost every living organism uses the same code

Question 31

Why is a universal genetic code beneficial?

Answer 31

It allows species to transfer genes between species

Question 32

How do we produce insulin (via recombinant gene transfer)?

Answer 32

Take a human cell with an insulin gene
Insert it in a plasmid
Insert the plasmid in a transgenic bacteria
Grow in a culture and extract

Question 33

What is the start codon?

Answer 33

AUG