Unit 1-Structure And Replication Of DNA

Question 1

Unit or molecules that DNA or RNA are made of?

Answer 1

Nucleotides

Question 2

3 parts of a nucleotide

Answer 2

Phosphate, deoxyribose sugar, and a base

Question 3

What determines the genetic code?

Answer 3

The base sequence

Question 4

What holds the nucleotides together in a strand of DNA ?

Answer 4

Strong chemical bonds (covalent)

Question 5

Which parts of nucleotides are joined together to form a strand?

Answer 5

Phosphate of one nucleotide and the deoxyribose sugar, on another nucleotide.

Question 6

What holds the bases in adjacent strands together?

Answer 6

Weak hydrogen bonds hold the bases together

Question 7

What is at the 3’ end of a DNA strand?

Answer 7

A deoxyribose sugar

Question 8

What is at the 5’ end of a DNA strand?

Answer 8

A phosphate

Question 9

What end can nucleotides be added to?

Answer 9

The 3’ end.

Question 10

How many different nucleotides are there?

Answer 10

4 different nucleotides

Question 11

What are the 4 different bases?

Answer 11

Adenine, Cytosine, Guanine and Thymine

Question 12

The two strands of DNA are antiparallel.

What does this mean?

Answer 12

One strand runs in a 5’ to 3’ direction and the other runs in a 3’ to 5’ direction.

Question 13

The distinctive shape of DNA molecules

Answer 13

Double helix

Question 14

Describe double helix shape of DNA

Answer 14

Two anti-parallel chains of nucleotides

Question 15

What is DNA arranged in?

Answer 15

Tightly coiled chromosomes.

Question 16

What is DNA polymerase?

Answer 16

An enzyme that adds new nucleotides to a growing strand of DNA.

Question 17

What is a primer?

Answer 17

Small sequence of single-stranded DNA required to start DNA replication.

Question 18

What strand has to be replicated in fragments?

Answer 18

Lagging strand (5’ end)

Question 19

Which strand is synthesised continuously

Answer 19

Leading strand (3’ end)

Question 20

Why is the 5’ end called the lagging strand?

Answer 20

Replication happens slower than the 3’ end.

Question 21

Why is the 3’ end called the leading strand?

Answer 21

Replication happens more quickly

Question 22

What is DNA ligase?

Answer 22

Ligase is an enzyme that joins all the DNA fragments together once they are all in place.

Question 23

For DNA replication to occur, what must the nucleus contain?

Answer 23

Primers
DNA (Template)
Enzymes (Ligase and DNA Polyemrase)
Nucleotides (the 4 types)
ATP

Question 24

Where does DNA replication occur?

Answer 24

In the nucleus.

Question 25

Steps in DNA replication

Answer 25

1. DNA molecule unwinds
2. Hydrogen bonds between the adjacent bases are broken
3. Free-floating nucleotides in the nucleus join onto their complementary bases.

Question 26

Which end of the DNA can nucleotides be added to?

Answer 26

The 3’ end.

Question 27

How can you recognise the 3’ and 5’ ends of a DNA strand?

Answer 27

The 5’ end at the phosphate end

The 3’ end at the deoxyribose end

Question 28

Why is DNA replication important?

Answer 28

It ensures that when the cell divides, each daughter cell will inherit an identical copy of the DNA.

Question 29

What does PCR stand for?

Answer 29

Polymerase Chain Reaction

Question 30

What is the function of the PCR?

Answer 30

PCR amplifies DNA
(Creates many copies of a piece of DNA).

Question 31

What is the role of primers in PCR?

Answer 31

Complementary primers for specific target DNA sequences are used.

Question 32

What are the steps involved in PCR?

Answer 32

DNA is heated (92–98°C) to separate/denature the DNA strands.

Cooled (50–65 °C) to allow the primers to bind to the target sequence of DNA.

Heat tolerant DNA polymerase (70-80°C) then adds nucleotides to the primers (at the 3’ end of the original DNA strands).

Repeated cycles of heating and cooling amplify the region of DNA.

Question 33

What are the practical uses of PCR?

Answer 33

Solve crimes - provide more DNA to analyse.

Diagnosing genetic disorders.

Settling paternity disputes using DNA profiling.