Structure And Replication Of DNA

Question 1

What does the base sequence of DNA form?

Answer 1

The genetic code

Question 2

What is DNA composed of?

Answer 2

DNA is composed of nucleotides containing deoxyribose sugar, phosphate and a base.

Question 3

What is a nucleotide?

Answer 3

A nucleotide is an organic molecule composed of a nitrogenous base, a deoxyribose sugar and a phosphate group.

Question 4

What forms the sugar phosphate backbone?

Answer 4

Strong chemical bonds between the phosphate ( 5’ ) and the deoxyribose sugar ( 3’ )

Question 5

What do sugar phosphate bonds hold together?

Answer 5

Sequences of nucleotides that form DNA

Question 6

What are the four bases on DNA?

Answer 6

Adenine, Thymine, Cytosine and Guanine

Question 7

What are the base pairing rules on DNA?

Answer 7

Cytosine bonds with Guanine and Adenine bonds with Thymine

Question 8

What are the complementary bases between nucleotides joined together by?

Answer 8

Hydrogen bonds

Question 9

What is the term used to describe how both strands of DNA run in opposite directions to eachother?

Answer 9

Antiparallel

Question 10

What is meant by antiparallel?

Answer 10

Antiparallel is a term used to describe how each strand of DNA runs in opposite directions ( one runs from the 5’ end to the 3’ end and the other runs from the 3’ end to the 5’ end )

Question 11

What is a term to describe the structure of DNA?

Answer 11

Double stranded Antiparallel helix

Question 12

When does DNA replication take place?

Answer 12

DNA replication takes place prior to cell division

Question 13

What enzyme unwinds DNA

Answer 13

Helicase

Question 14

What is the first stage in DNA replication?

Answer 14

The hydrogen bonds between bases are broken to form two template strands

Question 15

What is a primer and what is its role in DNA replication?

Answer 15

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

Question 16

What enzyme replicates DNA?

Answer 16

DNA Polymerase

Question 17

What is the function of DNA polymerase?

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 is there a leading and lagging strand?

Answer 18

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

Question 19

What enzyme joins fragments together?

Answer 19

Ligase

Question 20

What is PCR?

Answer 20

PCR ( polymerase chain reaction ) amplifies DNA using complementary primers for specific target sequences

Question 21

What is the use of primers in PCR?

Answer 21

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 22

What is PCR in terms of cycles?

Answer 22

PCR is repeated cycles of heating and cooling to amplify the target region of DNA

Question 23

What is stage 1 of PCR?

Answer 23

DNA is heated to 95 degrees celcius in order to break the hydrogen bonds between strands

Question 24

What is stage 2 of PCR?

Answer 24

DNA is cooled to 60 degrees celcius in order to allow primers to bind to specific target sequences

Question 25

What is stage 3 of PCR?

Answer 25

DNA is heated to 75 degrees celcius in order to allow * heat tolerant * DNA polymerase to replicate the region of DNA

Question 26

What are three uses of PCR?

Answer 26

3 uses:
Settling paternity suits
Solving crimes
Diagnosing genetic disorders