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Genetics and Evolution > DNA Replication > Flashcards

DNA Replication Flashcards

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Biology 101 flashcards
1
Q

What is a genome?

A

A complete set of DNA within a cell or organism

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2
Q

How many base pairs are in the human genome?

A

3.2 billion base pairs

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3
Q

How many chromosomes are in a human somatic cell?

A

46

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4
Q

What are the three stages of the cell life cycle?

A

Interphase, mitosis and cytokinesis

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5
Q

What is interphase?

A

A phase of cell growth and DNA replication

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6
Q

What is mitosis?

A

The process of DNA separation

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7
Q

What is cytokinesis?

A

The splitting of a parent cell to form two daughter cells

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8
Q

What are the three stages of interphase?

A

G1, S, and G2

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9
Q

What happens in the G1 phase?

A

All cellular contents, excluding the chromosomes, are duplicated

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10
Q

What happens in the S phase?

A

Each chromosome is duplicated

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11
Q

What happens in the G2 phase?

A

The cell checks the duplicated chromosomes, and repairs any mistakes

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12
Q

What is the longest phase of interphase?

A

G1

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13
Q

What is a mutation?

A

A change in the DNA sequence of an organism

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14
Q

What is genetic mosaicism?

A

The presence of two or more cell lines with different genotypes from a single zygote; result of a mutation

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15
Q

What disease is an example of genetic mosaicism?

A

Down syndrome

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16
Q

How does genetic mosaicism work in people with Down syndrome?

A

Some cells have a normal amount of 46 chromosomes, whereas some have 47 chromosomes

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17
Q

What is a zygote?

A

A fertilised egg cell formed from the combination of a female and a male gamete

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18
Q

What is a gamete?

A

A reproductive cell

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19
Q

What is a somatic cell?

A

All cell types in the body that are not germ cells

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20
Q

What are the two germ cells?

A

Egg cells and sperm cells

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21
Q

What are some examples of continuously dividing tissues?

A

Skin, GI epithelia, bone marrow

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22
Q

What are some examples of slowly dividing tissues?

A

Liver, kidney, pancreas

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23
Q

What are some examples of non-dividing tissues?

A

Myocardial tissues, central nervous system tissues

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24
Q

What was the experiment name that proved which model DNA replicated by?

A

The Meselson & Stahl experiment

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25
Q

What model does DNA replicate by?

A

Semi-conservative

26
Q

What is conservative replication?

A

Two strands of the parent DNA act as templates for new strands, and then recombine

27
Q

What is semi-conservative replication?

A

Two strands of the parent DNA separate and act as templates for new strands. The template strand and new strand combine

28
Q

What is dispersive replication?

A

Each strand contains a mixture of old and newly synthesised DNA

29
Q

What was the heavy isotope in which the E.coli was originally cultured in in the Meselson & Stahl experiment?

A

15N

30
Q

What was the light isotope in which the E.coli was transferred to in the Meselson & Stahl experiment?

A

14N

31
Q

What was added to the extracted E.coli DNA before centrifugation in the Meselson & Stahl experiment?

A

Caesium chloride

32
Q

What were the results from the Meselson & Stahl experiment after the first E.coli replication?

A

One band in the middle of the tube. This was a mixture of 14N and 15N. This ruled out conservative replication

33
Q

What were the results from the Meselson & Stahl experiment after the second E.coli replication?

A

One band in the middle (14N and 15N) and one band at the top (only 14N). This ruled out dispersive replication

34
Q

With each successive generation in the Meselson & Stahl experiment, what happens to the amount of 14N DNA and 15N DNA?

A

The amount of new DNA (14N) increases and the parent DNA (15N) is diluted out

35
Q

Where does DNA replication begin?

A

The origin of replication

36
Q

What direction does DNA replication occur?

A

It is bidirectional

37
Q

Where does DNA replication end?

A

At the terminator

38
Q

What do the replication forks form as DNA replication occurs?

A

A replication bubble

39
Q

What does topoisomerase do?

A

It is an enzyme that relieves the stress in the DNA backbone by breaking, swivelling, and rejoining the DNA strands

40
Q

What does DNA helicase do?

A

It is an enzyme that untwists the double helix at the replication fork to separate the parent strands

41
Q

What does DNA primase do?

A

It is an enzyme that synthesises RNA primers that attach to the template strand to initiate DNA polymerase

42
Q

What does DNA polymerase (III) do?

A

Continues DNA replication at the RNA primers by synthesising a complementary DNA strand by adding nucleotides at the 3’ end

43
Q

What does DNA polymerase (I) do?

A

It is an enzyme that adds DNA nucleotides where RNA primers were originally located

44
Q

What does DNA ligase do?

A

It is an enzyme that closes up the DNA strand once replication has finished

45
Q

What do single-stranded binding proteins do?

A

They bind to the parent strands to stabilise them and prevent re-pairing

46
Q

What does exonuclease do?

A

They are enzymes that remove RNA primers from the DNA strands

47
Q

What direction is DNA synthesised?

A

In the 5’ to 3’ direction

48
Q

Are nucleotides added at the 5’ or 3’ end?

A

3’

49
Q

What are the strands called in DNA replication?

A

The leading strand and the lagging strand

50
Q

What strand is replicated continuously in the direction of the replication fork?

A

The leading strand

51
Q

What strand is replicated in segments in the opposite direction to the replication fork?

A

The lagging strand

52
Q

What are the segments in which DNA is synthesised on the lagging strand called?

A

Okazaki fragments

53
Q

How long are Okazaki fragments in eukaryotic cells?

A

100-200 nucleotides long

54
Q

How long are RNA primers?

A

5-10 nucleotides long

55
Q

Why must RNA primers be added before DNA polymerase can work?

A

DNA polymerase can only recognise and elongate double-stranded sequences

56
Q

DNA synthesis during replication is fastest on which of the strands?

A

Synthesis of the lagging and leading strand occur simultaneously, but the lagging strand is slightly delayed

57
Q

Why are triphosphate molecules chemically reactive?

A

Because the triphosphate tails have an unstable cluster of negative charge

58
Q

What happens to the nucleotide when DNA polymerase catalyses the addition of a deoxyribonucleotide to the OH group at the 3’ end?

A

The deoxyribonucleotide is dehydrated and two phosphate groups are lost. The lost groups form a pyrophosphate molecule

59
Q

What happens when pyrophosphate becomes hydrolysed to two molecules of phosphate?

A

Energy is released

60
Q

What is the only difference between ATP and dATP?

A

The sugar molecule

61
Q

What is dATP?

A

Deoxyadenosine triphosphate, a nucleotide used in cells for DNA replication

Genetics and Evolution (14 decks)

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