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

1.2 DNA & its replication Flashcards

1
Q

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

A

nucleotides

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2
Q

How many different components are each nucleotide made of ?

A

3

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3
Q

What does each nucleotide include?(3)

A

a phosphate group
a deoxyribose sugar
a base

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4
Q

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

A

the base

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5
Q

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

A

Adenine
Thymine
Guanine
Cytosine

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6
Q

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

A

double helix

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7
Q

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

A

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

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8
Q

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

A

weak hydrogen bonds between bases on each strand

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9
Q

What are the base pairs?

A

adenine-thymine

guanine-cytosine

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10
Q

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

A

a 3’ and a 5’ end

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11
Q

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

A

opposing directions to each other

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12
Q

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

A

anti-parallel

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13
Q

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

A

it terminates in a phosphate group

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14
Q

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

A

it terminates in a deoxyribose sugar group

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15
Q

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

A

2

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16
Q

How many hydrogen bonds does the base pair

G-C have?

17
Q

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

A

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

18
Q

What are nucleosomes?

A

DNA + histones

19
Q

What are nucleotides?

A

subunits which make up each strand of DNA

20
Q

What is meant by double helix?

A

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

21
Q

What are chromosomes?

A

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

22
Q

What is a histone?

A

protein around which DNA is coiled and packaged

23
Q

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

A

An exact copy of DNA called DNA replication

24
Q

What does the process of DNA replication produce?

A

2 identical DNA molecules from 1 parent molecule

25
Q

What is stage 1 of DNA replication ?

A

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
Q

What is stage 2 of DNA replication?

A

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
Q

What is stage 3 of DNA replication?

A

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

28
Q

What is stage 4 of DNA replication ?

A

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
Q

What is stage 5 of DNA replication ?

A

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

30
Q

What is stage 6 of DNA replication ?

A

These fragments are then joined together by the enzyme ligase

31
Q

What is the source of energy of DNA replication ?

32
Q

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

A

Simultaneously at several replication forks along its length

33
Q

What is DNA polymerase ?

A

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

34
Q

What is DNA ligase ?

A

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

35
Q

What is the lagging strand ?

A

Strand of DNA replicated in fragments which must be joined together

36
Q

What is the leading strand?

A

New segment of DNA replicated continuously from template DNA

37
Q

What is a primer ?

A

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

38
Q

Describe the semi-conservative replication theory?

A

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

Higher Biology Unit 1: Human Cells (8 decks)

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