DNA

Question 1

What is DNA make up of?

Answer 1

A phosphate group
Pentose sugar 2-deoxyribose
base

Question 2

Why is the phosphate group an ion?

Answer 2

One of the oxygens has a negative charge

Question 3

What are the 4 different bases ?

Answer 3

Adenine
Thymine
Cytosine
Guanine

Question 4

What is a polynucleotide chain?

Answer 4

Nucleotides joined together

Question 5

What is the sugar-phosphate backbone?

Answer 5

Covalent bonds form between the phosphate group of one nucleotide and the sugar of another

Question 6

What type of reaction forms a sugar-phosphate backbone?

Answer 6

Condensation polymerisation releasing a molecule of water

Question 7

What type of bond forms between a phosphate and sugar in a sugar-phosphate backbone?

Answer 7

Phosphodiester bond

Question 8

How many polynucleotide strands join to make DNA?

Answer 8

2

Question 9

What is the double helix structure of DNA?

Answer 9

2 polynucleotide strands spiralled together and held together by hydrogen bonds between the bases

Question 10

Which base pairs with A?

Answer 10

T

Question 11

Which base pairs with T?

Answer 11

A

Question 12

Which base pairs with C?

Answer 12

G

Question 13

Which base pairs with G?

Answer 13

C

Question 14

How many hydrogen bonds form between A and T?

Answer 14

2

Question 15

How many hydrogen bonds form between C and G?

Answer 15

3

Question 16

How does complimentary base pairing work?

Answer 16

A hydrogen bond forms between a partially positive hydrogen atom and a die pour of electrons on a nearby oxygen or nitrogen.
They have to be the right distance apart

Question 17

What parts of adenine bond with which parts of thymine?

Answer 17

Adenine N = H thymine

Adenine H = O thymine

Question 18

What parts of guanine bond to which parts on cytosine/

Answer 18

Guanine H = O cytosine
Guanine H = N cytosine
Guanine O = H cytosine

Question 19

What is the formula of cisplatin?

Answer 19

[PtCl2(NH3)2]

Question 20

What shape is cisplatin?

Answer 20

Square planar

Question 21

How does cisplatin work as an anticancer drug?

Answer 21

1) Nitrogen atom on guanine base in DNA forms a co-ordinate bond with cisplatin’s platinum ion, replaces one of the chloride ion ligands
2) A second nitrogen atom from a nearby guanine molecule can bond to the platinum and replace the second chloride ion
3) The presence of the cisplatin complex is bound to the DNA strands causes the strands to kink and this means the DNA strands cant unwind and the strand can be copied properly

Question 22

What are the adverse effects of using cisplatin?

Answer 22

• Hair loss
• Suppress the immune system
• causes kidney damage

Question 23

Why are there adverse effects of cisplatin?

Answer 23

Cisplatin binds to DNA in normal cells as well as cancer cells

Question 24

How can the effects of using cisplatin be lessened?

Answer 24

Giving very low dosages

Target the tumour directly

Question 25

Even though there are negative effects of cisplatin, why is it still used?

Answer 25

The positive long term effects outweigh the negative short-term effects