Key Area 2

Question 1

What does DNA stand for?

Answer 1

deoxyribonucleic acid

Question 2

What does a molecule of DNA consist of?

Answer 2

2 strands ( double helix ) each composed of repeating units called nucleotides

Question 3

What does a nucleotide consist of?

Answer 3

Deoxyribose Sugar
Phosphate
Base

Question 4

what are the 4 bases?

Answer 4

Adenine
Thymine
Guanine
Cytosine

Question 5

How many different nucleotides can there be?

Answer 5

4

Question 6

What does the base sequence of DNA determine?

Answer 6

the genetic code

Question 7

How many other bases can each base connect with?

Answer 7

1

Question 8

what are the complimentary base pairs?

Answer 8

A-T

G-C

Question 9

how are the base pairs held together?

Answer 9

Hydrogen bonding

Question 10

how are the nucleotides held together?

Answer 10

chemical bonds

Question 11

How can the 2 strands be described?

Answer 11

anti-parallel

Question 12

Where is there a strong chemical bond?

Answer 12

between the sugar of one nucleotide and the phosphate of another

Question 13

What is the strong chemical bond between sugar and phosphate known as?

Answer 13

the sugar phosphate backbone

Question 14

which shape do the 2 stands form?

Answer 14

double helix shape

Question 15

which 2 ends does a molecule of DNA have?

Answer 15

3’ and 5’ end

Question 16

Describe the deoxyribose sugar

Answer 16

It is a pentagon shape and has 5 carbons.
- carbon 1 attaches to the base
- carbon 3 attaches to a phosphate from a different
nucleotide forming the sugar phosphate backbone
- carbon 5 attaches to the phosphate from the same
nucleotide

Question 17

What happens to DNA before cell division?

Answer 17

DNA is replicated by enzyme - DNA polymerase

Question 18

What is the first step of replicating DNA?

Answer 18

Double helix is unwound and hydrogen bonds between bases are broken to form 2 template strands

Question 19

What does DNA polymerase require to begin replication?

Answer 19

Primers

Question 20

What is a primer?

Answer 20

A short strand of nucleotides

Question 21

Where does a primer bind?

Answer 21

The 3’ end of the template DNA strand allowing the enzyme polymerase to add DNA nucleotides

Question 22

Where are nucleotides added?

Answer 22

The 3’ end of the new DNA strand which is forming

Question 23

How are nucleotides added?

Answer 23

Using complimentary base pairing

Question 24

Why are the 2 strands replicated differently?

Answer 24

DNA polymerase can only add nucleotides in one direction and the strands are anti parallel

Question 25

How are the 2 strands replicated?

Answer 25

Leading strand - continuously

Lagging strand - in fragments

Question 26

How are the fragments of DNA joined?

Answer 26

Enzyme - ligase

Question 27

What ‘seals’ the leading strand

Answer 27

okazaki fragments

Question 28

What is PCR?

Answer 28

Polymerase Chain Reaction

Question 29

What does PCR do?

Answer 29

Replicates a section of DNA

Question 30

How does PCR replicate sections of DNA?

Answer 30

Amplifies DNA using complementary primers for specific target sequences

Question 31

What are primers in PCR?

Answer 31

Short strands of nucleotides complementary to specific target sequences at the 2 ends of the region of DNA to be amplified

Question 32

Summarize PCR

Answer 32

Repeated cycles of heating and cooling to amplify the target region of DNA

Question 33

What are the 3 stages of PCR?

Answer 33

1. DNA is heated between 92’C and 98`C to separate
   the strands
2. It is cooled to between 50C and 65C to allow
   primers to bind to target sequences
3. It is heated to between 70C and 80C for heat
   tolerant DNA polymerase to replicate the region of
   DNA

Question 34

How many times is the PCR cycle repeated?

Answer 34

Until the desired quantity is produced

Question 35

Give 3 practical uses of applications of PCR

Answer 35

Solving crimes
Paternity testing
Diagnosing Genetic Disorders