1.2 DNA & Replication

Question 1

What is each strand of DNA made up of repeating units called

Answer 1

Nucleotides

Question 2

How many components does each nucleotide have

Answer 2

3 different components

Question 3

What does each component of nucleotides include

Answer 3

A phosphate group, a deoxyribose sugar and a base

Question 4

What are the four chemical bases in DNA

Answer 4

Adenine, guanine, cytosine and thymine

Question 5

Describe the structure of DNA

Answer 5

It’s doubled stranded and wound into a helix shape

Question 6

What are nucleotides

Answer 6

Sub units which make up each strand of DNA

Question 7

How are the nucleotides joined together

Answer 7

By a chemical bond where the deoxyribose of one nucleotide joins with the phosphate of another nucleotide called a sugar phosphate bond which forms a sugar phosphate backbone

Question 8

How are the two strands held together

Answer 8

By weak hydrogen bonds which join the bases together

Question 9

What does each base have

Answer 9

A specific complementary base partner

Question 10

What do both strands of DNA have

Answer 10

A 5’ and a 3’ end running in opposing directions

Question 11

What can the DNA strands be described as

Answer 11

Anti parallel

Question 12

What does the 5’ end of the strand begin with

Answer 12

A phosphate

Question 13

What does the 3’ end of a strand start with

Answer 13

A deoxyribose sugar

Question 14

Why must the vast amount of DNA be packed

Answer 14

So it can fit into the cells nucleus

Question 15

Where is DNA tightly coiled around

Answer 15

Protein molecules called histones and arranged into chromosomes

Question 16

What is DNA replication

Answer 16

The process by which 2 identical DNA molecules are made from 1 parent molecule to make an exact copy of DNA

Question 17

What is the first stage of DNA replication

Answer 17

The double helix of DNA unwinds and unzips with hydrogen bonds between bases breaking

Question 18

What is the second stage of DNA replication

Answer 18

A primer attached to the complementary target sequence at the start of the sequence of bases to be replicated

Question 19

What is the third stage of DNA replication

Answer 19

This allows the enzyme DNA polymerase to synthesise a new strand of DNA by adding nucleotides complementary to the template strand

Question 20

What is the fourth stage of DNA replication

Answer 20

DNA polymerase only adds nucleotides to the 3’ end of the growing strand. This means that DNA polymerase works in a 5’ to a 3’ direction. One strand is replicated continuously and is known as the leading strand

Question 21

What is the fifth stage of DNA replication

Answer 21

The other strand is synthesised in fragments in a 3’ to 5’ direction and is known as the lagging strand

Question 22

What is the sixth stage of DNA replication

Answer 22

The fragments of the lagging strand are joined by the enzyme ligase