1.5.8 The Process of Semi-Conservative Replication Flashcards

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1
Q

DNA replication occurs in preparation for

A

mitosis

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2
Q

DNA replication occurs in preparation for mitosis, when

A

a parent cell divides to produce two genetically identical daughter cells – as each daughter cell contains the same number of chromosomes as the parent cell, the number of DNA molecules in the parent cell must be doubled before mitosis takes place

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3
Q

DNA replication occurs during the what phase of the cell cycle

A

S phase (which occurs during interphase, when a cell is not dividing)

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4
Q

The enzyme

A

helicase

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5
Q

The enzyme helicase

A

unwinds the DNA double helix

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6
Q

The enzyme helicase unwinds the DNA double helix by

A

breaking the hydrogen bonds

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7
Q

The enzyme helicase unwinds the DNA double helix by breaking the hydrogen bonds between

A

the base pairs on the two antiparallel polynucleotide DNA strands

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8
Q

The enzyme helicase unwinds the DNA double helix by breaking the hydrogen bonds between the base pairs on the two antiparallel polynucleotide DNA strands to form

A

two single polynucleotide DNA strands

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9
Q

Each of these single polynucleotide DNA strands acts as

A

a template

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10
Q

Each of these single polynucleotide DNA strands acts as a template for

A

the formation of a new strand

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11
Q

Each of these single polynucleotide DNA strands acts as a template for the formation of a new strand made from

A

free nucleotides

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12
Q

ach of these single polynucleotide DNA strands acts as a template for the formation of a new strand made from free nucleotides that are attracted to

A

the exposed DNA bases

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13
Q

Each of these single polynucleotide DNA strands acts as a template for the formation of a new strand made from free nucleotides that are attracted to the exposed DNA bases by

A

base pairing

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14
Q

The new nucleotides are then joined together by

A

DNA polymerase

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15
Q

The new nucleotides are then joined together by DNA polymerase which

A

catalyses condensation reactions to form a new strand

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16
Q

The original strand and the new strand joined together through

A

hydrogen bonding between base pairs to form the new DNA molecule

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17
Q

This method of replicating DNA is known as semi-conservative replication because

A

half of the original DNA molecule is kept (conserved) in each of the two new DNA molecules

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18
Q

Semi-conservative replication of DNA

A
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19
Q

In the nucleus, there are free

A

nucleotides

20
Q

In the nucleus, there are free nucleotides which contain

A

three phosphate groups

21
Q

Free nucleotides, which contain three phosphate groups, are known as

A

nucleoside triphosphates or ‘activated nucleotides’

22
Q

The extra phosphates activate

A

the nucleotides

23
Q

The extra phosphates activate the nucleotides, enabling them to

A

take part in DNA replication

24
Q

The bases of the free nucleoside triphosphates align with their

A

complementary bases

25
Q

The bases of the free nucleoside triphosphates align with their complementary bases on

A

each of the template DNA strands

26
Q

Which enzyme synthesises new DNA strands from the two template strands

A

DNA polymerase

27
Q

The enzyme DNA polymerase synthesises

A

new DNA strands from the two template strands

28
Q

The enzyme DNA polymerase synthesises new DNA strands from the two template strands, it does this by

A

catalysing condensation reactions between the deoxyribose sugar and phosphate groups of adjacent nucleotides within the new strands

29
Q

The enzyme DNA polymerase synthesises new DNA strands from the two template strands, it does this by catalysing condensation reactions between the deoxyribose sugar and phosphate groups of adjacent nucleotides within the new strands, creating

A

the sugar-phosphate backbone of the new DNA strands

30
Q

DNA polymerase cleaves (breaks off) the two extra phosphates and uses the energy released to create

A

the phosphodiester bonds (between adjacent nucleotides)

31
Q

Hydrogen bonds then form between

A

the complementary base pairs of the template and new DNA strands

32
Q

Nucleotides are bonded together by DNA polymerase to create the new complementary DNA strands

A
33
Q

DNA polymerase can only build the new strand in one direction

A

5’ to 3’ direction

34
Q

As DNA is ‘unzipped’ from the 3’ towards the 5’ end, DNA polymerase will

A

attach to the 3’ end of the original strand

35
Q

As DNA is ‘unzipped’ from the 3’ towards the 5’ end, DNA polymerase will attach to the 3’ end of the original strand and

A

move towards the replication fork (the point at which the DNA molecule is splitting into two template strands)

36
Q

This means the DNA polymerase enzyme can synthesise the leading strand

A

continuously

37
Q

This template strand that the DNA polymerase attaches to is known as

A

the leading strand

38
Q

The other template strand created during DNA replication is known as

A

the lagging strand

39
Q

On the lagging strand, DNA polymerase moves away from

A

replication fork (from the 5’ end to the 3’ end)

40
Q

This means the DNA polymerase enzyme can only synthesise the lagging DNA strand in

A

short segments (called Okazaki fragments)

41
Q

A second enzyme known as

A

DNA ligase

42
Q

A second enzyme known as DNA ligase is needed to

A

join these lagging strand segments together to form a continuous complementary DNA strand

43
Q

DNA ligase does this by

A

catalysing the formation of phosphodiester bonds

44
Q

DNA ligase does this by catalysing the formation of phosphodiester bonds between the segments to create

A

a continuous sugar-phosphate backbone

45
Q

The synthesis of the complementary strands occurs slightly differently on the leading and lagging template strands of the original DNA molecule that is being replicated

A