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BMS242 CELL AND MOLECULAR > DNA REPAIR > Flashcards

DNA REPAIR Flashcards

1
Q

WHAT IS THE FUNCTION OF EXONUCLEASES

A

‘PROOF READ’ DNA TO CORRECT ERRORS MADE IN REPLICATION

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2
Q

WHAT TYPES OF DAMAGE CAN DNA BE EXPOSED TO

A
  1. THERMAL DEGRADATION
  2. METABOLIC BYPRODUCTS
  3. ENVIRONMENTAL SUBSTANCES
  4. RADIATION
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3
Q

WHY IS IT IMPORTANT THAT DNA CAN BE REPAIRED COMPARED TO OTHER MOLECULES

A

DNA HAS TWO MOLECULES ONLY AND HARBOURS MOST INFORMATION

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4
Q

WHICH BASES ARE CONSIDERED PURINES

A

ADENINE AND GUANINE

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5
Q

WHAT STRUCTURALLY MAKES PURINES DIFFERENT TO PYRAMIDINES

A

TWO CARBON NITROGEN RING BASES

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6
Q

WHICH BASES ARE CONSIDERED PYRIMADINES

A

CYTOSINE, THYMINE AND URACIL

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7
Q

WHY IS THE CYTOSINE GUANINE PAIR A MORE STABLE MOLECULE

A

BECAUSE IT CAN FORM 3 H BONDS

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8
Q

WHAT STRUCTURALLY STOPS THYMINE FORMING 3 H BONDS

A

CH3 GROUP

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9
Q

DEAMINATION (ADDITION OF H2O AND REMOVAL OF NH3) OF CYTOSINE RESULTS IN WHAT

A

CONVERSION TO URACIL

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10
Q

THERE ARE SITES ON ALL BASES THAT ARE VULNERABLE TO WHAT

A
  1. HYDROLYTIC ATTACK

2. OXIDATIVE DAMAGE

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11
Q

URACIL IS ALMOST CHEMICALLY IDENTICAL TO WHICH BASE

A

THYMINE

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12
Q

WHAT IS THE DIFFERENCE BETWEEN URACIL AND THYMINE

A

ONE METHYL GROUP

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13
Q

FAILURE TO UNDERTAKE DNA REPAIR RESULTS IN

A

MUTATION

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14
Q

IF REPAIR IS NOT UNDERTAKEN BEFORE REPLICATION WHAT OCCURS

A

ONE OF THE NEW DAUGHTER STRANDS WOULD CARRY THE MUTATION

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15
Q

WHAT ARE THE TWO CATEGORIES OF MUTATION

A

TRANSVERSION

TRANSITION

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16
Q

WHAT IS TRANSVERSION

A

MUTATION OF A PURINE FOR A PYRIMIDINE OR VICE VERSA

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17
Q

WHAT IS A TRANSITION

A

MUTATION OF A PURINE FOR A DIFFERENT PURINE OR PYRIMIDINE FOR ANOTHER PYRMIDINE

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18
Q

HOW MANY TYPES OF TRANSVERSION IS THERE

A

4 TYPES

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19
Q

HOW MANY TYPES OF TRANSITION IS THERE

A

2 TYPES

20
Q

IS TRANSVERSION OR TRANSITION MORE COMMON

A

TRANSITION MUTATIONS ARE MORE COMMON

21
Q

TRANSITION MUTATIONS ARE ……….. LIKELY TO RESULT IN AMINO ACID SUBSTITUTIONS

A

LESS

22
Q

MULTIPLE POTENTIAL …………… ALLOW FOR THE ………… AMINO ACID

A

CODONS

SAME

23
Q

MOST OF THE TIME MUTATION IN THE FIRST OR SECOND BASE WILL RESULT IN WHAT

A

AMINO ACID SUBSTITUTION

24
Q

MUTATIONS IN THE THIRD BASE OF A CODON, MOST ARE …………………….. ALTERNATIVES

A

TRANSITIONAL

25
Q

WHAT OCCURS AS A RESULT OF UV LIGHT

A

PHOTOLYTIC CONVERSION

26
Q

WHAT DOES PHOTOLYTIC CONVERSION CAUSE

A

PYRMIDINE DIMERS

27
Q

WHAT IS A PYRIMIDINE DIMER

A

THE DOUBLE BONDS IN PYRIMIDINES ARE HIGHLY REACTIVE AND WHEN UV LIGHT BREAKS THE BONDS, THEY FORM BOND WITH THEMSELVES INSTEAD OF THE COMPLIMENTARY PURINE

28
Q

HOW CAN PHOTOLYTIC CONVERSION BE REPAIRED

A

NUCLEOTIDE EXCISION REPAIR (NER/LONG PATCH) USES AN EXCISION NUCLEASE TO CLEAVE A 12 NUCLEOTIDE LONG SSDNA AROUND THE DIMER. DNA HELICASE UNWINDS IT FROM THE STRAND SO IT CAN BE EXPOSE TO DNA POLYMERASE AND SEALED BACK WITH DNA LIGASE.

29
Q

HOW IS DEPURINATION REPAIRED

A

VIA THE BASE EXCISION REPAIR PATHWAY (BER/SHORT PATCH)

30
Q

WHAT IS THE BER PATHWAY

A

REPAIR ENZYMES(GLYCOSYLASES) FIND AN INAPPROPRIATE BASE, IT IS CLEAVED
AN ENDONUCLEASE AND PHOSPHODIESTERASE REMOVE THE BACKBONE
DNA POLYMERASE ADDS THE NEW NUCLEOTIDE
DNA LIGASE SEALS IT IN

31
Q

WHAT METHOD DO GLYCOSYLASES USE TO FIND ERRORS

A

BASE FLIPPING

32
Q

WHAT HAPPENS WHEN DNA POLYMERASE REACHES ABNORMAL DNA THAT HAS NOT BEEN REPAIRED

A

IT RELEASES FROM THE STRAND AND TRANS-LESIONAL DNA POLYMERASE BINDS VIA ASSEMBLY FACTORS

33
Q

WHAT IS THE DISADVANTAGE OF TRANS LESIONAL DNA POLYMERASE

A

THEY LACK PRECISION AND ARE MORE LIKELY TO MAKE ERRORS WHEN CROSSING THE POINT OF DAMAGE

34
Q

WHAT IS THE MAIN CAUSE OF BASE SUBSTITUTION AND SINGLE NUCLEOTIDE DELETION MUTATIONS

A

TRANS LESIONAL DNA POLYMERASE

35
Q

WHAT ARE THE ADVANTAGES OF TRANS LESIONAL DNA POLYMERASE

A
  1. ITS MISTAKES ARE A DRIVER OF EVOLUTION

2. IT IS THE BEST CASE SCENARIO IN TERMS OF REPAIR THAT HAS NOT HAPPENED PRIOR TO REPLICATION

36
Q

WHY ARE DOULE STRANDED BREAKS HAZARDOUS

A

THERE IS NO TEMPLATE FOR REPAIR

37
Q

WHAT ARE THE CAUSES OF DS BREAKS

A

IONISING RADIATION
REPLICATION ERRORS
OXYGEN RADICALS

38
Q

WHAT ARE THE TWO MECHANISMS THAT EXIST TO REPAIR DS BREAKS

A
  1. NON HOMOLOGOUS END JOINING

2. HOMOLOGOUS RECOMBINATION

39
Q

WHAT HAPPENS IN NON HOMOLOGOUS END JOINING

A

THE ENDS OF THE BROKEN DNA MOLECULES ARE JOINED TOGETHER AFTER EACH END IS PROCESSES

40
Q

WHAT ARE THE DISADVANTAGES OF NON HOMOLOGOUS END JOINING

A

THERE IS A CHANCE OF LOSS OF NUCLEOTIDES

THERE IS A CHANCE THAT THERE IS JOINING OF THE WRONG STRANDS

41
Q

WHAT IS HOMOLOGOUS RECOMBINATION

A

NUCLEASE DIGESTS THE ENDS OF BROKEN STRANDS

THE STRAND INVADES THE HOMOLOGOUS STRAND ALLOWING TEMPLATED REPLICATION IN ORDER TO GET AN ACCURATE COPY

42
Q

WHAT IS THE ADVANTAGE OF HOMOLOGOUS RECOMBINATION

A

IT IS MORE ACCURATE

43
Q

WHAT IS THE DISADVANTAGE OF HOMOLOGOUS RECOMBINATION

A

YOU GET LOSS OF HETEROZYGOSITY AS THE LOST ALLELE MAY HAVE BEEN DIFFERENT FROM WHAT IS BEING COPIED

44
Q

GIVE AN EXAMPLE OF A DISEASE THAT ARISES FROM LACK OF DNA REPAIR ENZYMES

A

XERODERMA PIGMENTOSUM

45
Q

FAILURES IN DNA REPAIR SYSTEMS HAVE STRONG LINKS TO WHAT

A

CANCERS

BMS242 CELL AND MOLECULAR (14 decks)

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