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IB Bio HL > D1.1 DNA Replication > Flashcards

D1.1 DNA Replication Flashcards

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Biology 101 flashcards
1
Q

Reasons for DNA replication

A
  • cell division
  • reproduction
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2
Q

semi coneservative replication

A

Type of DNA replication in which each double strand of DNA contains one strand of the original DNA and one strand of newly synthesised DNA

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3
Q

activated nucleotide

A

has 3 phosphate groups

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4
Q

Semi conservative replication outlines

A
  1. Hydrogen bonds between bases break
  2. free nucleotides are present in the nucleus
  3. free neucleotides pair up with complementary exposed bases
  4. new strand is linked together
  5. now two DNA molecules => each one old and one new strand
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5
Q

evidence for semi conservative replication

A
  • cultured e.colibacteria in the presence of heavy nitrogen isotope (15N)
  • bacterial culture transferred to fresh medium = nitrogen replaced with 14N
  • after one generation/division of bacteria the resulting DNA strand consisted of one strand 14N and one strand 15N
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6
Q

Gel electrophoresis

A

molecules are seperated by their size and amount of charge

uses an electrical current to move molecules through a semisolid medium

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7
Q

Facts about gel electrophoresis

A
  • DNA/RNA has negative charge -> moves to positive electrode
  • 250-30000 bp in length fragments
  • samples with fragments are loaded into small wells
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7
Q

Key points of gel electrophoresis

A
  • DNA must be colored with ethidium bromide
  • seperates by charge and size
  • consistency of gel allows seperation of the DNA fragements by size
  • DNA must travel through soaces between polymers
  • smaller pieces can slip through easily => travel further
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8
Q

PCR Test stages

A
  1. Denaturing to seperate DNA strands

primer, DNA fragments, polymerase and nucleotoides added to thermocycler (95 degrees)

  1. Annealing of primers

primers join to their complementary basses at 55-68 degrees

  1. synthesis of DNA

temperature increased to 72 degrees; optimum of DNA polymerase= Taq attached to nucelotides of seperated DNA

=> repeats multiple times to amplify

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9
Q

Advantages of PCR

A
  • very rapid
  • does not require living cells
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10
Q

PCR

A

polymerase chai. reaction in which DNA is amplified for further processing or study

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11
Q

applications of PCR

A
  • Tissue Typing = donor & recepient can be matched to reduce rejection
  • Detection of oncogenes = detect type of mutual leading to cancer
  • detecting mutations = genetic diseases
  • identifying viral infections = verify the type
  • monitoring spread of infectious disease
  • forensiuc science = identify criminals
  • research = extinct organisms
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11
Q

Things needed for PCR

A
  • Taq polymerase (DNA polymerase)
  • small DNA sample
  • thermocycler
  • primers
  • nucleotides
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12
Q

DNA profiling stages

A
  1. extract DNA from sample
  2. digest sample using resitriction endonuclease
  3. seperate DNA fragments using electrophoresis
  4. DNA seperated into single strand susing alkaline solution
  5. DNA fragments transferred to nylon membrane by southern blotting
  6. Hybridisation of DNA probes added to label fragments
  7. development (placed into x ray)
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13
Q

Lagging strand

A

DNA strand that is synthesised discontinuously in short fragments

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13
Q

Directionality of DNA replication

A

5 -> 3
* phosphate group on the 5th C of the pentose sugar covelently bonds to OH on 3rd C
* DNA polymerase III adds the 5 end of a DNA nucleotide to 3 end

14
Q

DNA

Leading strand

A

DNA strand that is synthesised continuously in the 5 to 3 direction

15
Q

How the lagging strand operates

A
  • DNA polymerase III replicates new strand in sections
  • repeatedly move further along the strand to continue replication
  • sections of disconnected DNA = okazaki fragments
  • DNA ligase joins Okazaki Fragments together
16
Q

Gyrase

A

moves ahead of helicases, relieving tension created by the unwinding and unzipping of DNA

16
Q

Helicase

A

unwinds & unzips the DNA molecule by breaking H bonds holding compl. bases together

17
Q

Ligase

A

catalyses formation of ohosphodiester bonds between okazaki fragments

18
Q

DNA polymerase I

A

removes RNA nucelotides of the primers and replaces them with correct DNA nucelotides

18
Q

DNA primase

A

attracts small RNA primers, made up of RNA nucleotides to the template strand = allows DNA polymerase III to attach and begin assembling free nucleotides = new DNA strand

19
Q

DNA polymerase III

A

assembles new dtrand of DNA by placing new nucleotides in the correct sequence according to the base sequence of the template strand and comp. base pairing rule

20
Q

DNA proofreading

A

DNA polyemerase III proofreads newly built DNA = removes incorrectly placed nucleotides & replaces with correct one

21
Q

DNA proofreading steps

A
  1. DNA polymerase III adds incorrect nucelotide while building new DNA
  2. DNA polymerase III identifies the error as it does not match the base pair
  3. DNA polymerase III removes incorrect nucleotide
  4. DNA polymerase III adds correct nucleotide
22
Q

Which enzymes are needed for the leading strand

A

DNA polymerase, DNA Primase, one RNA primer

23
Q

What enzymes are needed for the lagging strand

A

DNA polymerase, DNA primase, RNA primers

IB Bio HL (13 decks)

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