1.2 DNA & its replication Flashcards Preview

Higher Biology Unit 1: Human Cells > 1.2 DNA & its replication > Flashcards

Flashcards in 1.2 DNA & its replication Deck (38):
1

What are the repeating units which each strand of DNA is made of?

nucleotides

2

How many different components are each nucleotide made of ?

3

3

What does each nucleotide include?(3)

a phosphate group
a deoxyribose sugar
a base

4

What is the only thing that makes one nucleotide different from the other?

the base

5

What are the 4 different types of base that exist in DNA?

Adenine
Thymine
Guanine
Cytosine

6

What name is given to DNA because it consists of 2 strands wound together in to a spiral ?

double helix

7

What are the nucleotides which makeup up each strand joined by?

a strong chemical bond between the deoxyribose sugar of one group and the phosphate of the next forming a sugar-phosphate backbone.

8

What are the two strands of the DNA held together by?

weak hydrogen bonds between bases on each strand

9

What are the base pairs?

adenine-thymine
guanine-cytosine

10

What do both strands of DNA in the double helix have?

a 3' and a 5' end

11

What do both strands of DNA in the double helix run in?

opposing directions to each other

12

What is DNA described as because it runs in opposing directions to each other?

anti-parallel

13

How can the 5' end of a strand be identified ?

it terminates in a phosphate group

14

How can the 3' end of a strand be identified?

it terminates in a deoxyribose sugar group

15

How many hydrogen bonds does the base pair A-T have?

2

16

How many hydrogen bonds does the base pair
G-C have?

3

17

The vast amount of DNA present must be packaged to allow it to fit into the nucleus of cells. How is this achieved?

DNA is tightly coiled around protein molecules called histones and arranged to form chromosomes.

18

What are nucleosomes?

DNA + histones

19

What are nucleotides?

subunits which make up each strand of DNA

20

What is meant by double helix?

2 strands held together by hydrogen bounds wound into a spiral conformation.

21

What are chromosomes?

structures contained within the nucleus of cells consisting of tightly wound DNA and proteins.

22

What is a histone?

protein around which DNA is coiled and packaged

23

What must be made before cells divide and what is this process called?

An exact copy of DNA called DNA replication

24

What does the process of DNA replication produce?

2 identical DNA molecules from 1 parent molecule

25

What is stage 1 of DNA replication ?

For DNA replication to take place, the double helix of DNA must unwind/uncoil and unzip, with hydrogen bonds between complimentary bases breaking to present two template strands

26

What is stage 2 of DNA replication?

A primer, a short strand of nucleic acid, binds to the complementary target sequence at the start of the sequence of bases to be replicated.

27

What is stage 3 of DNA replication?

This allows the enzyme DNA polymerase to synthesise a new strand of DNA by adding the bases complimentary to the template strand

28

What is stage 4 of DNA replication ?

DNA polymerase can only add nucleotides to the 3' end of the growing strand due to the configuration of nucleotides. DNA polymerase therefore only works in a 5' to 3' direction.. As a consequence, one strand is replicated continuously and is known as the leading strand.

29

What is stage 5 of DNA replication ?

The other is synthesised in fragments in the opposite direction and is known as the lagging strand.

30

What is stage 6 of DNA replication ?

These fragments are then joined together by the enzyme ligase

31

What is the source of energy of DNA replication ?

ATP

32

When a long chromosomes is being replicated how do these events occur?

Simultaneously at several replication forks along its length

33

What is DNA polymerase ?

Enzyme which adds free nucleotides to the 3' end of a growing strand

34

What is DNA ligase ?

Enzyme that joins fragments of DNA together to form a long continuous strand

35

What is the lagging strand ?

Strand of DNA replicated in fragments which must be joined together

36

What is the leading strand?

New segment of DNA replicated continuously from template DNA

37

What is a primer ?

Small sections of DNA/nucleic acid, complimentary to the template strand, which allows DNA polymerase to start replication

38

Describe the semi-conservative replication theory?

Each daughter DNA molecule made in DNA replication will consist of half the original strand plus half a newly synthesised strand