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BMS1062 > DNA Replication > Flashcards

DNA Replication Flashcards

1
Q

What is cDNA?

A

DNA synthesised from single stranded RNA (e.g. mRNA or micro RNA) template in a reaction catalysed by the enzyme reverse transcriptase. cDNA is often used to clone eukaryotic genes in prokaryotes

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2
Q

What is centrifugation?

A

A process that is used for the separation of fluids, gas or liquid based on density

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3
Q

What is conservative replication?

A

A type of replication that results in one of the daughter molecules containing all the parent DNA and the other daughter molecule containing none of it

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4
Q

What is dispersive replication?

A

A type of replication that results in all off the daughter molecules having segments of DNA from their parent and the rest is new DNA

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5
Q

What is DNA cloning?

A

(1) the act of making may identical copies of a DNA molecule - the amplification of a particular DNA sequence. (2) also, the isolation of a particular stretch of DNA from the rest of the cells genome

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6
Q

What is a DNA library?

A

Collection of cloned DNA molecules representing either an entire genome (genomic library) or complementary DNA copies of the mRNA produced by a cell (cDNA library)

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7
Q

What is DNA polymerase?

A

An enzyme that synthesises DNA by joining nucleotides together using a DNA template as a guide

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8
Q

What is gel electrophoresis?

A

A laboratory method used to seperate mixtures of DNA, RNA, or proteins according to molecular size

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9
Q

What is a genomic library?

A

Collect of cloned DNA molecules representing an entire genome

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10
Q

What is helicase?

A

A type of enzyme that separates double-stranded DNA into single strands allowing each strand to be copied

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11
Q

What is hybridisation?

A

The process whereby two complementary nucleic acid strands forms a base paired duplex DNA-DNA, DNA-RNA, or RNA-RNA molecule. Forms the basis of a powerful technique for detecting specific nucleotide sequences

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12
Q

What is ligase?

A

A specific type of enzyme that facilitates the joining of DNA strands together by catalysing the formation of a phosphodiester bond

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13
Q

What is a plasmid vector?

A

Small, circular molecules of double stranded DNA derived from plasmids that occur naturally in bacterial cells; widely used for gene cloning

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14
Q

What is a poly a tail?

A

A stretch of RNA that has only adenine bases

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15
Q

What is polymerase chain reaction?

A

Technique for amplifying specific regions of DNA by the user sequence specific primers and multiple cycles of DNA synthesis, each cycle being followed by a brief heat treatment to separate complementary strands

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16
Q

What is primase?

A

An enzyme that synthesises a short strand of RNA on a DNA template, producing a primer for DNA synthesis

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17
Q

What is a primer?

A

A short strand of RNA that serves as a starting point for DNA synthesis

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18
Q

What is recombinant DNA technology?

A

Collection of techniques by which DNA segments from different sources are combined to make new DNA, often called recombinant DNA. Recombinant DNAs are widely used in the cloning of genes, in the genetic modification of organisms, and in the production of large amounts of rare proteins

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19
Q

What is replication cell senescence?

A

Phenomenon observed in primary cell cultures in which cell proliferation slows down and irreversibly halts

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20
Q

What are restriction nucleases?

A

One of the large number of nucleases that can cleave a DNA molecule at any site where a specific short sequence of nucleotides occurs. Extensively used in recombinant DNA technology

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21
Q

What is semi-conservative replication?

A

A type of replication that results in both daughter molecules having a parent strand of DNA and a new strand. DNA synthesis is semi-conservative

22
Q

What is shelterin?

A

A protein complex known to protect telomeres in many eukaryotes from DNA repair mechanisms, as well as regulate telomerase activity

23
Q

What are single-stand binding proteins?

A

A protein that binds to the single strands of the opened up DNA helix, preventing helical structures from reforming while the DNA is being replicated

24
Q

What are somatic cells?

A

Any cell of a plant or animal other than the cells of the germ line

25
Q

What is strand-directly mismatch repair?

A

A proofreading system that removes DNA replication errors missed by the DNA polymerase proofreading exonuclease. It detects the potential for DNA helix distortion from noncomplememtary base pairs the recognises the excises the mismatch in the newly synthesised strand and resynthesises the excised segment using the old strand as a template

26
Q

What is taq polymerase?

A

An enzyme found in the bacillus Thermus aquaticus, which lives in hot springs; it is heat resistant and thus can endure the high temperatures of the polymerase chain reaction

27
Q

What are tautomeric forms?

A

Constitutional isomers of the main forms of nucleotides that may cause mistakes in base pairing

28
Q

What is telomerase?

A

Enzyme that elongates telomere sequences in DNA, which occurs at the ends of eukaryotic chromosomes

29
Q

What is a telomere?

A

End of a chromosome, associated with a characteristic DNA sequence that is replicated in a special way. Counteracts the tendency of the chromosome to otherwise shorter. With each round of replication

30
Q

How many origins of replications occur in prokaryotes?

A

One

31
Q

How many origins of replication occur in eukaryotes?

A

Multiple

32
Q

What enzyme opens up the DNA?

A

Helicase

33
Q

What is responsible for stabilising unwound DNA?

A

Single-strand binding protein

34
Q

Which enzyme is responsible for adding nucleotides to the growing polynucleotide chain? What direction does it synthesise in?

A

DNA polymerase

5’ to 3’

35
Q

How do enzymes know where to start replicating the DNA?

A

The replication sites have short sequences to attract the initiator proteins and stretches of DNA that are easy to open

36
Q

Is eukaryotic or prokaryotic replication quicker?

A

Prokaryotic

37
Q

Replication requires RNA primers, what enzyme(s) add these primers to the DNA?

A

DNA primase

38
Q

How are old primers removed from the DNA?

A

They are erased by a combined action of DNA polymerase and RNase H

39
Q

What does the clamp loader do?

A

Holds the DNA polymerase onto the DNA as it moves

40
Q

Which enzyme is responsible for relieving helical winding?

A

DNA topoisomerases

41
Q

How often does a mistake occur in DNA replication?

A

1 in a billion

42
Q

In the rare tautomeric form, what base can C pair with?

A

A instead of G

43
Q

After covalent binding, what is the next error correcting reaction?

A

Exonucleolytic proofreading by DNA polymerase in the 3’ to 5’ direction

44
Q

How does exonucleolytic prrofreading work?

A

Correct nucleotide pairing has a higher affinity for polymerase. If an incorrect pairing occurs, the polymerase chews back to create a base-paired 3’ -OH end on the primer strand. It then continues the process of adding nucleotides correctly

45
Q

What would happen if the strand-directed mismatch repair system was not able to differentiate between the new strand and old strand?

A

It would correct the wrong nucleotide 50% of the time

46
Q

What allows the strand-directed mismatch repair system to differentiate between the new strand an the old strand?

A

Newly synthesised lagging-strand DNA transiently contains nicks (that haven’t yet been sealed by DNA ligase) and such nicks provide the signal that directs the mismatchprrofreading to the appropriate strand

47
Q

What enzyme adds telomere sequences to the end of chromosomes?

A

Telomerase

48
Q

What is the proteins that form a protective chromosome cap called?

A

Shelterin

49
Q

What does shelterin do?

A

Shelterin hides telomeres from the cell’s damage detectors that continually monitor DNA

50
Q

What happens when there is no telomere sequence left?

A

The cell enters replicative cell senescence, withdrawing them permanently from the cell cycle and preventing them from dividing

BMS1062 (9 decks)

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