Unit 1-Structure And Replication Of DNA

Question 1

What units or molecules are DNA and RNA made of?

Answer 1

Nucleotides.

Question 2

What are the three parts of a nucleotide?

Answer 2

Phosphate, deoxyribose sugar and base.

Question 3

What determines the genetic code?

Answer 3

The base sequence.

Question 4

What holds nucleotides together in a DNA strand?

Answer 4

Strong covalent bonds.

Question 5

Which parts of nucleotides join to form the sugar‑phosphate backbone?

Answer 5

Phosphate of one nucleotide joins to the deoxyribose of the next.

Question 6

What holds the bases on opposite strands together?

Answer 6

Weak hydrogen bonds

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

To which end can nucleotides be added?

Answer 9

The 3’ end.

Question 10

How many different DNA nucleotides are there?

Answer 10

Four.

Question 11

What are the four DNA bases?

Answer 11

Adenine, cytosine, guanine and thymine.

Question 12

What does it mean that DNA strands are antiparallel?

Answer 12

One runs 5’ → 3’ and other runs 3’ → 5’

Question 13

What is the distinctive shape of DNA?

Answer 13

Double helix

Question 14

Describe the double helix structure

Answer 14

Two antiparallel chains of nucleotides

Question 15

How is DNA arranged in cells?

Answer 15

Tightly coiled chromosomes.

Question 16

What is DNA polymerase?

Answer 16

Enzyme that adds nucleotides to a growing DNA strand.

Question 17

What is a primer?

Answer 17

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

Question 18

Which strand is replicated in fragments?

Answer 18

Lagging strand

Question 19

Which strand is synthesised continuously?

Answer 19

Leading strand

Question 20

Why is the 5’ end called the lagging strand?

Answer 20

Replication is slower and occurs in fragments.

Question 21

Why is the 3’ end called the leading strand?

Answer 21

Replication is continuous and faster.

Question 22

What is DNA ligase?

Answer 22

Enzyme that joins DNA fragments together.

Question 23

What must the nucleus contain for DNA replication?

Answer 23

Primers, DNA template, enzymes (polymerase and ligase), nucleotides and ATP

Question 24

Where does DNA replication occur?

Answer 24

In the nucleus.

Question 25

What are the steps in DNA replication?

Answer 25

1. DNA unwinds 2. Hydrogen bonds break and strands separate 3. Free nucleotides join to complementary bases

Question 26

Which end of DNA can nucleotides be added to?

Answer 26

The 3’ end.

Question 27

How can you recognise the 3' and 5' ends?

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

Ensures each daughter cell receives an identical copy of DNA.

Question 29

What does PCR stand for?

Answer 29

Polymerase Chain Reaction

Question 30

What is the function of PCR?

Answer 30

Amplifies DNA (makes many copies).

Question 31

What is the role of primers in PCR?

Answer 31

Complementary primers bind to target sequences.

Question 32

What are the steps of PCR?

Answer 32

Heat to 92–98°C to separate strands Cool to 50–65°C so primers bind Heat to 70–80°C so heat‑tolerant DNA polymerase adds nucleotides Repeated cycles amplify DNA

Question 33

Practical uses of PCR

Answer 33

Crime investigation Diagnosing genetic disorders Paternity testing