UNIT 1 - KA2

Question 1

What are the three parts In a nucleotide (DNA)

Answer 1

Phosphate , deoxyribose sugar , base

Check jotter for diagram

Question 2

What is the full name for DNA

Answer 2

Deoxyribonucleic Acid

Question 3

Sugar phosphate backbone

Answer 3

• a strong chemical bond joins the nucleotides it forms between the deoxyribose sugar for one and the phosphate group of the next

Question 4

What type of bonds hold the two strands of DNA together

Answer 4

Weak hydrogen bonds between bases hold the two strands of DNA together

Question 5

Anti parallel strands

Answer 5

• DNA strands have 2 ends
• a 3’ end with deoxyribose sugar at the end
• a 5’ end with phosphate at the end
• the two strands run anti parallel to each other

Question 6

What is the shape of a DNA molecule

Answer 6

The DNA molecule takes the shape of a twisted double helix with the sugar phosphate backbone (upright on the outside and the base pairs on the inside)

Question 7

What does the base sequence of DNA do

Answer 7

The base sequence of DNA forms the genetic code

Question 8

Draw a diagram of the structure of DNA

Answer 8

Check jotter for answer

Question 9

When does DNA replication take place

Answer 9

DNA replication takes place just prior to cell division

Question 10

Which enzyme is responsible for DNA replication

Answer 10

DNA polymerase is the enzyme responsible for DNA replication

Question 11

What does DNA polymerase require to start replication

Answer 11

DNA polymerase needs primers to start replication

Question 12

What is a primer

Answer 12

A primer is a short strand of nucleotides which binds to the 3’ end of the template DNA strand

Question 13

Briefly describe what DNA polymerase does

Answer 13

DNA polymerase adds DNA nucleotides using complementary base pairing to the deoxyribose (3’) end of the new DNA strand which is forming

Question 14

How should the two new DNA strands be made

Answer 14

The two strands of a DNA molecule run antiparallel to each other. Therefore the two new strands of DNA must be made in different ways

Question 15

What happens prior to cell division (1st step of DNA replication)

Answer 15

Prior to cell division, DNA is replicated by an enzyme called DNA polymerase. DNA polymerase needs primers to start replication

(A primer is a short strand of nucleotides which binds to the 3’ end of the template DNA strand allowing DNA polymerase to add DNA nucleotides)

Question 16

How are the two template strands formed (2nd step of DNA replication)

Answer 16

DNA is unwound and hydrogen bonds between bases are broken to form template strands

Question 17

How does DNA polymerase add DNA nucleotides (3rd step of DNA replication)

Answer 17

DNA polymerase adds DNA nucleotides , using complementary base pairing to the deoxyribose 3’ end of the new DNA strand which is forming

Question 18

Why are the two strands replicated in different ways (4th step of DNA replication)

Answer 18

DNA polymerase can only add DNA nucleotides in one direction resulting in the leading strand being replicated continuously and the lagging strand being replicated in fragments

Question 19

Which enzyme joins DNA on the lagging strand (5th step of DNA replication)

Answer 19

The fragments of DNA on the lagging strand are joined together by an enzyme called ligase

Question 20

Draw a diagram of the two new template DNA strands

Answer 20

Check jotter

Question 21

What is the technique polymerase chain reaction

Answer 21

PCR or polymerase chain reaction is a technique used to AMPLIFY DNA outside the body (in vitro)

Question 22

What are PCR primers (think of stage 2 of PCR)

Answer 22

PCR primers are short strands of nucleotides which are complementary to specific target sequences at the two ends of the region of DNA to be amplified

Question 23

Where does heat tolerant DNA polymerase add nucleotides to

Answer 23

Heat tolerant DNA polymerase adds nucleotides to the primers at the 3’ end of the original strand of DNA , leading to the replication of that region of DNA

Question 24

What are the three applications of PCR

Answer 24

• forensics / solve crimes
• settle paternity suits
• diagnose genetic disorders

Question 25

What does the test tube which target DNA is added to contain

Answer 25

Target DNA added to test tube containing heat tolerant DNA polymerase , two types of primer + four types of DNA nucleotide

Question 26

What is the first step of PCR thermal cycle

Answer 26

STEP 1 - DNA heated to between 92-98 degrees C to separate the DNA strands

Question 27

What is the second step of PCR thermal cycle

Answer 27

STEP 2 - mixture cooled to between 50-65 degrees C to allow primers to bind to complementary target sequences

Question 28

What is the third step of PCR thermal cycle

Answer 28

STEP 3 - mixture heated to between 70-80 degrees C for HEAT TOLERANT DNA polymerase to amplify the region of DNA

Question 29

How many times should the PCR thermal cycle be repeated

Answer 29

Procedure repeated 20-30 more times DNA becomes amplified

Question 30

What does a primer allow

Answer 30

allows polymerase to add DNA nucleotides