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Biology - biological molecules + cells > 3.1.5.2 DNA Replication > Flashcards

3.1.5.2 DNA Replication Flashcards

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1
Q

When must DNA be replicated in a cell

A

Before the cell divides

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2
Q

What’s cell division know as
What’s it for
E.g

A

Mitosis
For growth + repair

E.g replacing skin cells daily, red blood cells after donating blood

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3
Q

Why does a cell have to copy all of the DNA inside the nucleus before it can divide

A

To become 2 new cells with each s complete copy of DNA

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4
Q

What does DNA replication involve copying

A

The sequence of organic bases (genome) to reproduce the code again

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5
Q

What’s the genome

A

Sequence of organic bases

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6
Q

Why are bases difficult to access even though they need to be

A

As they’re protected by a helix

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7
Q

What must happen to the hydrogen bonds between complimentary base lakes so DNA CNS be replicated

A

They must be broken

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8
Q

What enzyme breaks hydrogen bonds between. Omplimentsry base pairs

A

DNA Helicase

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9
Q

What does the DNA helicase cause to happen once hydrogen bonds are broken

A

The helix to uncoil

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10
Q

What happens to the bases once the helix uncoils

A

They’re exposed so can be copied

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11
Q

What are the original strands in the double helix known as

A

Parental strands

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12
Q

What enzyme follows helicase

A

DNA polymerase

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13
Q

What does DNA polymerase do to the parental strands

A

Adds free (single) nucleotides to each exposed strand

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14
Q

What does DNA polymerase use the exposed strands as

A

Templates

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15
Q

Where does DNA polymerase assemble the free nucleotides from

A

Cytoplasm

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16
Q

Why are the new daughter strands complementary

A

Due to the base pair rule

17
Q

What do New strands need to form between their nucleotides
How
What’s produced

A

Phosphodiester bonds
Condensation reactions
Water

18
Q

What bonds form between old and new strands to form a double helix again

A

Hydrogen bonds

19
Q

What does DNA polymerase work in

A

Pairs

20
Q

What direction does DNA polymerase add nucleotides in

Why so specific?

A

3’ -> 5’direction

Due to substrate

21
Q

DNA polymerase works 3’->5’ on one template strand, but what does it do on the other

A

Can work in the 3-5 direction by assembling the free nucleotides in ‘chunks’

22
Q

Why must DNA polymerase work in the 3-5 direction

A

As the antiparallel arrangement of nucleotides means they are the right shape to fit in the active site of DNA polymerase

23
Q

3 adaptations DNA has for replication

A

Strong phosphodiester bonds - strands remain intact
Hydrogen bonds easily broken - strands can unwind (exposing bases)
Base pair rule - accurate copies made

24
Q

Who came up with 2 theories for DNA replication in 1953

A

Watson and crick

25
Q

What are the 2 DNA replication theories

A

Conservative replication

Semi-conservative replication

26
Q

What happens in conservative replication

A

Original DNA molecules stay intact

New nucleotides assemble to form a separate, new DNA molecule

27
Q

What happens in semi conservative replication

A

The original DNA splits - each strand acts as a template for a new molecule

28
Q

2 reasons why it’s called semi-conservative replication

A

Each new DNA molecule contains 50% original DNA

Both new molecules are identical - to each other and the original

29
Q

Who investigated Watson and cricks’ theory

A

Meselson and stahl

30
Q

Method of meselson and stahl’s experiment

A

Grew bacteria in a growth medium containing heavy nitrogen (15N)

Then put the same bacteria into a medium containing light nitrogen (14N) for 1 replication generation

Then extracted and spun the DNA In a centrifuge - separating the DNA based on its mass

31
Q

What did meselson and stahl use for their experiment

A

Isotopes of nitrogen (15N heavy nitrogen and 14N light nitrogen)

32
Q

Why did meselson and stahl use bacteria

A

As it reproduces quickly

DNA is accessible as it isn’t in the nucleus

33
Q

What did the original bacteria have in their DNA as they replicated originally

A

Heavy nitrogen

34
Q

How does bacteria divide

A

Binary fission

35
Q

How does a centrifuge spin

A

Very fast

Biology - biological molecules + cells (16 decks)

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