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BIO HL > D1.1 DNA replication > Flashcards

D1.1 DNA replication Flashcards

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1
Q

What is semi conservative replication

A

when one strand comes from the original chromosome and the other is newly synthesized at the end of DNA replication to form a new double helix
Each original strand forms a new helix with a new strand

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2
Q

What is conservative replication

A

when an entirely new double helix is formed alongside the original with no unzipping of DNA
1 helix is completely original
1 helix is completely new

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3
Q

How can a high degree of accuracy be maintained when copying base sequences

A

through complementary base pairing and semi conservative replication

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4
Q

what does helicase do

A

unwinds the DNA double helix at one region, breaking hydrogen bonds and temporarily keeping the strands separated

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5
Q

how do both strands of DNA act as templates in replication

A

complementary nucleotides line up opposite each base on the exposed strands
hydrogen bonds then form

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6
Q

What are the purposes of DNA polymerase

A

catalyses a condensation reaction between sugar and phosphate groups of nucleotides, forming the new strands
also proofreads the new DNA for mistakes

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7
Q

what are the uses for analysing DNA to identify individuals

A

forensics and genetic relatedness

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8
Q

What is the use of polymerase chain reaction

A

they allow small fragments of DNA to be copied repeatedly in a fully automated process

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9
Q

What enzyme is used in PCR

A

a heat tolerant DNA polymerase enzyme known as tag polymerase

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10
Q

How can amplified DNA be separated

A

through gel electrophoresis, allowing genotypes of different individuals to be compared

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11
Q

what are the limitations of PCR

A

knowledge of the amino acid sequence of a desired genes is needed to synthesize nucleotide primers
non target sequence may be amplified because short nucleotide sequences may not be specific enough

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12
Q

what are DNA primers

A

short sequences of single stranded DNA, made synthetically with base sequences complementary to one end of DNA

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13
Q

what is gel electrophoresis

A

a process thats used to separate molecules such as proteins and nucleic acids
important for DNA sequencing

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14
Q

What is the separation of nucleic acid fragments/ proteins in gel electrophoresis due to

A

migration of these molecules through a sieve like medium ( agarose gel), essentially size
the electrical charge that molecules carry ( phosphate has negative charge, so migrate to positive side), basically charge

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15
Q

how can fragments be identified after separation in gel electrophoresis?

A

through gene probes and DNA stains

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16
Q

what is a gene probe

A

single stranded DNA that is complementary to that of a particular gene, must be radioactive so it can be identified

17
Q

what is a DNA stain

A

locate the position of all DNA fragments once applied
stains can be ethidium bromide, or methylene blue

18
Q

what is genetic profiling

A

used to identify organisms, species or individuals using DNA
uses both PCR and gel electrophoresis

19
Q

what are Variable number tandem repeats

A

VNTR’s are short base sequences that show variation between individuals in terms of number of repeats
they are major lengths of non coding DNA used in genetic profiling

20
Q

features of VNTRs

A

dont code for proteins are scattered throughout the length of the DNA molecule in clusters
half comes from each parent
everyone has unique sequence of nucleotides in our DNA

21
Q

how are genetic profiles produced

A

a sample of DN is cut with a restriction enzyme that acts close to the VNTR region
electrophoresis then used to separate fragments, resulting in a pattern of bands

22
Q

what is the process of southern blotting

A

copy of distrbuted DNA fragments on nylon membrane ( through southern blotting)
heat treatment of nylon membrane binds DNA to it
DNA probes added to bind to particular DNA
Nylon membrane overlaid with xray film which is fogged by emissions from probes
film is developed to show position of fragments

23
Q

what are the applications of genetic fingerprinting

A

identification of suspects
identification of corpses
determining paternity

24
Q

Which way does DNA polymerase move along the strand

A

synthesizes in 5’ to 3’ direction and moves along the template strand in the opposite direction

25
Q

why does DNA polymerase move in a certain direction

A

because otherwise it would be unable to proofread, allows it to function as a self correcting enzyme

26
Q

what is replication initiated by

A

an RNA primer

27
Q

what are replication forks

A

semi conservative replication is initiated at many points along the double helix, known as replication forks

28
Q

what is the result of enzyme helicase

A

bubbles form due to hydrogen bonds being split apart

29
Q

what does DNA gyrase do

A

assists in reducing tension and prevents separate strands from rejoining

30
Q

what do single strand binding proteins do

A

they attach and prevent separate strands from rejoining, allowing unwound section to act as templates for the synthesis of complementary DNA strands

31
Q

why do DNA strands only elongate in the 5’ to 3’ direction

A

because nucleotides can only be added to the free 3’ direction

32
Q

what happens in the leading strand

A

exposed 5’ to 3’ is the leading strand
DNA polymerase III adds nucleotides to free 3’ end in same direction as replication fork
continous process as helicase continues to move and new template is exposed

33
Q

what is the function of the primer

A

a short length of RNA that is synthesized by primase where the new DNA can start from ( initial nucleotide chain)

34
Q

what happens in the lagging strand

A

replication is discontinuous
strands synthesized in opposite direction
Okazaki fragments are formed, each primed separately
allows both strands to replicate at the same time

35
Q

what are Okazaki fragments

A

shorts lengths of DNA created due to discontinuous process

36
Q

what is the function of DNA ligase

A

present in the lagging strand to join the fragments together

37
Q

function of enzymes in DNA replication

A

RNA primer formed by primase and then DNA polymerase III attached nucleotides to the RNA primer, forming a fragment
DNA polymerase I replaced the RNA nucleotides at the start of each fragment with DNA nucleotides
Enzyme DNA ligase joins the Okazaki fragments together

38
Q

How is DNA polymerase III involved in DNA proofreading?

A

removes any mismatched base from the 3’ terminal which is then replaced with the correct nucleotide
ensures any wrong nucleotides are removed before DNA replication proceeds

39
Q

How is proofreading carried out

A

by a nuclease that cleaves the phosphodiester bond

BIO HL (23 decks)

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