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Cells > DNA Replication > Flashcards

DNA Replication Flashcards

1
Q

What is the direction of DNA synthesis

A

DNA is always synthesised in the 5’ to 3’ direction

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2
Q

What direction are the parental template strands “run”

A

The template strands are run in the 3’ to 5’ direction

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3
Q

What are the characteristics of eukaryotic DNA replication

A

DNA replication occurs from multiple origins of replications (ori)
It is bidirectional (replicating both ways from the origin)

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4
Q

What is meant by DNA replication being semi discontinuous

A

The leading strand is continuously sythensised in its 5’ to 3’ direction
The lagging strand is dis continuously synthesised in its 5’ to 3’ direction (as Okazaki fragments)

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5
Q

What is Primase

A

Primase is an enzyme that makes an RNA primer (a starting point for DNA polymerisation)

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6
Q

What is DNA polymerase III

A

An enzyme that synthesises a new DNA strand by adding nucleotides complementary to the parallel template strand
It only synthesises in the 5’ to 3’ direction

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7
Q

What is the “head of the zipper” where Helicase is unwinding DNA called

A

The replication fork

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8
Q

What is topoisomerase

A

An enzyme that cuts and rejoins DNA strands to release tension generated by the unwinding of DNA strands

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9
Q

What is DNA polymerase

A

An enzyme that detects DNA/RNA hybrids, degrades the RNA component, and fills the gap with DNA nucleotides

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10
Q

What is DNA ligase

A

An enzyme that joins the newly synthesised fragments (Okazaki fragments, ends of leading strands, gaps between replication bubbles)
Bonds created are phosphodiester bonds

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11
Q

What are the two activities that DNA polymerase 1 carries out

A

RNase activity - recognises DNA/RNA hybrid and degrades RNA component
DNA polymerisation activity - Synthesises DNA by adding nucleic bases in the remaining gaps

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12
Q

What provides progressive addition of DNA nucleotides

A

DNA polymerase 3

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13
Q

What provides a starting point for nucleotide addition

A

Primase enzyme which synthesises RNA primer

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14
Q

What unwinds helical double strand of DNA

A

Helicase

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15
Q

What releases tension built up by the unwinding of DNA helix

A

Topoisomerase

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16
Q

What prevents the unwound double strands from reforming, and protects them from degradation

A

Single stranded binding protein

17
Q

What removes RNA primers, and fills the gaps with DNA nucleotides

A

DNA polymerase 1

18
Q

What joins the ends of newly synthesised fragments together (Okazaki fragments, ends of leading strand, intersections of replication bubbles)

A

DNA ligase

19
Q

When can DNA errors be repaired

A

During replication - through use of exonuclease
After replication - through use of endonuclease

20
Q

Which enzyme has a DNA proof reading mechanism

A

DNA polymerase 3 has a preoofreading mechanism, where by it checks newly inserted nucleotide bases against the template

21
Q

How are exonuclease errors removed

A

DNA polymerase 3 recognises damaged/incorrect DNA
Incorrect base is removed by the 3’ to 5’ exonuclease activity of DNA polymerase 3
DNA synthesis continues

22
Q

What is the process of exonuclease

A

Damaged/incorrect DNA is identified during DNA polymerisation
Incorrect nucleotide is removed by the 3’ to 5’ exonuclease activity of DNA polymerase 3
DNA synthesis continues

23
Q

What are examples of things than can cause DNA damage post replication

A

Incorrect inserted basses are not corrected by DNA polymerase 3
Radiation damage (e.g. UV light, falling inside Chernobyl)
Chemical modifications of bases (natural and chemical causes)

24
Q

What is the process for endonuclease

A

Damage/incorrect DNA is located
Damage, including some flanking regions, is removed by an endonuclease
A DNA polymerase synthesises new DNA
DNA ligase joins new DNA to existing DNA (phosphodiester bonds)

25
Q

What is the significance of a DNA error not being fixed

A

When the error carrying DNA helix is seperate for replication, both strands (including the error) will be used as a template. Hence the two parent strands will code the permanent DNA error onto the template strands and the error will be carried onto the two resulting new DNA strands. All future DNA molecules arising from this strand will carry this permanent error

26
Q

What is “in vitro” DNA synthesis and PCR

A

DNA replication in a test tube
Polymerase Chain Reaction

27
Q

What is the Polymerase Chain Reaction

A

“In Vitro” method of making multiple DNA copies so that there is enough DNA material to work with
Only “targeted” DNA region will be copied
Rapid exponential increase in DNA molecules
Method uses cycles of heating and cooling

28
Q

What are some applications for the Polymerisation Chain Reaction

A

Medical applications
Forensic Applications
Infectious disease detection and identification
Molecular biology research applications

29
Q

What are the 3 steps to polymerase chain reaction

A

Denaturation - Temperature is increased to seperate DNA strands
Annealing - Temperature is decreased to allow primers to base pair to complementary DNA template
Extension - Polymerase extends primer to form new (5’ to 3’) DNA strand

30
Q

What occurs upon repetition of polymerase chain reaction

A

Exponential Amplification of the region of interest

31
Q

What is the function of DNA template in PCR

A

DNA molecule to which complementary nucleotides can be matched to make identical copies via DNA synthesis

32
Q

What is the function of primers in PCR

A

Defines region of DNA molecule to be replicated
Provides free 3’ OH group - essential to initiate DNA synthesis

33
Q

What is the function of DNA polymerase in PCR

A

Enzyme which adds nucleotides (complimentary to DNA template) and joins them together using phosphodiester bond

34
Q

What is the function of dNTPs in PCR

A

Free nucleotides - the building blocks used by DNA polymerase

Cells (33 decks)

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