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Biology > DNA Replication & Repair > Flashcards

DNA Replication & Repair Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Base pair allows for ________

A

DNA Replication

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2
Q

Each strand of DNA that contains a certain type of nucleotide sequence can be a ______ used to make a new strand

A

Template (allows cells to replicate genes before dividing up)

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3
Q

Semiconservative replication

A

Since each parent strand of DNA is a template for each daughter strand of DNA double helix, the duaghter helix will have one of the parent strand (old strand strand) & a new strand

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4
Q

DNA synthesis begins at ______

A

Replication origins

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5
Q

Replication origins

A

Specific DNA sequence that initiator proteins bind to start DNA synthesis (unzip/ open up a DNA strand & its just an area where DNA is opened)

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6
Q

__________ form at each replication origin

A

Two replication forks

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7
Q

Replication fork

A

The y shaped junctions that allows a replication machine to move along the DNA (they continuously open DNA strands up in opposite direction)

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8
Q

__________ synthesizes DNA using a parental strand as a template

A

DNA polymerase (is whats copying the DNA strands as the replication forks is continuously opening up the DNA strand)

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9
Q

DNA polymerase 3

A

An enzyme that builds the new strand of DNA using the old strand as a template (Builds it in the 5’ to 3’ direction)

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10
Q

The new DNA strand is made (synthesized) in what direction by the DNA polymerase?

A

The DNA polymerase makes the new DNA strand in the 5’ to 3’ direction only (add a new nucleotide triphosphate)

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11
Q

The replication fork is ________ because at each replication fork one new DNA strand is made on a template that runs in 3’ to 5’ direction whereas the other new DNA strand is made in the 5’ to 3’ direction

A

Asymmetrical

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12
Q

Okazaki Fragments

A

Small DNA pieces that was made in the opposite direction of the replication fork (made in the 3’ to 5’ direction) & is made disconinuously, they ae the lagging strands

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13
Q

Lagging strand

A

The DNA strand that is made discontinuously

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14
Q

Leading strand

A

The DNA strand that made continuously

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15
Q

Since DNA polymerase only goes in the 5’ to 3’ direction it is able to be ________

A

Self - Correcting

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16
Q

What are the two reasons why DNA is able to be self-correcting and make no wrong base pairs (like A-G or C-T) ?

A
  1. The enzyme (DNA polymerase) carefully monitors the base-pairing between each incoming nucleotide triphosphate & template strand
  2. When DNA polymerase does make a rare mistake & add wrong base pairs togethers it can correct it through proofreading
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17
Q

________ occurs as each new DNA strand is made

A

Proofreading

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18
Q

Short lengths of _______ act as primers for DNA synthesis

A

RNA

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19
Q

Primers

A

A Short nucleic acid sequence that provides a starting point for DNA synthesis

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20
Q

The accuracy of DNA replication depends on the _________ to correctly base - pair the 3’ end before adding on more nucleotides

A

DNA polymerase

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21
Q

Primase

A

An enzyme that is used as a starting place to make a new strand of DNA, its made of a short RNA & uses the DNA strand as the template since the A in DNA can pair with the U in RNA the RNA fragment serves as a primer (Starting place) for DNA synthesis (Its a type of RNA polymerase)

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22
Q

RNA contains ______ instead of thymaine (T) but since _____ can pair with A, RNA primer is made on the DNA strand by base - pairing the same way as DNA

A

Uracil (U)

23
Q

_________ only starts the replication at the replication origins

A

RNA primer

24
Q

Need _______ to form a new strand of DNA from the lagging strands

A

DNA Ligase

25
Q

DNA ligase

A

An enzyme that joins the 5’ end phosphate of one okazi fragment to the adjacent 3’ end hydroxyl end of the next (Seals the gap within the strands)

26
Q

______ at a replication fork cooperate to form a replication machine

A

Proteins

27
Q

What protein (enzyme) continuously open/unzip DNA strand?

A

DNA helicases

28
Q

DNA helicases

A

An enzyme that breaks the hydrogen bond between the base

29
Q

Single-strand DNA-binding proteins

A

Prevents the DNA strand from zipping up back up

30
Q

DNA topoisomerases

A

Enzyme that relase the tension caused by the helicases continuously prying open DNA causing it to twist even more

31
Q

________ produces a single-strand cut in the DNA backbone which releases the tensions

A

DNA topoisomerase

32
Q

_________ replicates the ends of eukaryotic chromosomes

A

Telomerase

33
Q

Telomerase

A

Are enzymes attached to the end of a chromsome

34
Q

Telomerase uses its own _________ template which it uses to add multiply copies of repetitive DNA sequence to the lagging - strands so the lagging strand doesn’t get shorter & shorter so that DNA isn’t lost in each cell divison

A

RNA template

35
Q

________ & __________ prevents linear eukaryotic chromosomes from shortening with each cell division

A

Telomers & telomerase

36
Q

DNA damage occurs in cells since DNA molecules undergo _____ with other molecules

A

Collisions

37
Q

Depurination

A

Process where purine bases (A & G) is lost from DNA in the cells of the body (Just removes the purine bases)

38
Q

Deamination

A

Loss of a an amino group from a cytosine in DNA to produce the base Uracil

39
Q

Thymine dimer

A

Type of damage to DNA by UV radiation from the sun which causes covalent linkage between two adjacent pyrimidine bases

40
Q

What are the different types of chemical changes?

A
  1. Depurination
  2. Deamination
  3. Thymine dimer
41
Q

If chemical modification are left unpaired it can cause _________

A

Mutations

42
Q

What are the steps for repairing DNA?

A
  1. When the damage is recognized, nucleases will cut out the damage nucleotide sequence from the DNA strand leaving a gap on the strand
  2. A repair DNA polymerase binds the 3’ hydroxyl end of the cut DNA strand where the enzyme fill up the gap by making a complementary copy of the nucleotide sequence in the damage strand
  3. When the repair DNA polymerase filled up the gap the break in the sugar-phosphate backbone is fixed by DNA ligase
43
Q

A DNA _______ system removes replication errors that escape proofreading

A

Mismatch repair system

44
Q

Mismatch repair

A

Corrects the mistakes that were left after proofreading

45
Q

Mismatch

A

Mispaired nucleotide (like A-G or C-T)

46
Q

If nucleotides on one strand of DNA is damaged it can be fixed using _______________

A

Nucleotide sequence in the complementary strand as a template

47
Q

What are the strategies used to repair double-strand break?

A
  1. Nonhomologous end joinging
  2. Homologous Recombination
48
Q

Nonhomologous end joining

A

Sticking the broken ends back together before the fragment drift apart but also can lose nucleotides at the repair site as well (Risky process)

49
Q

Homologous Recombination

A

Flawlessly repairs DNA double -strand break (safer process)

50
Q

What is the steps for homologous steps?

A
  1. Nuclease digest the 5’ end of the broken strand
  2. Strand invasion by complementary base-pairng
  3. Repair polymerase synthsizes DNA using undamaged complementary DNA as a template
  4. Invading strand released complementary base-pairing allows broken helix to reform
  5. DNA synthesis using complementary strands from damaged DNA as a template
  6. DNA ligation
51
Q

SSB proteins

A

Protect the two separated DNA strand & stablize them which prevent them from snapping back together

52
Q

DNA replication occurs where in eukaryotic cell?

A

In the nucleus

53
Q

DNA polymerase 1

A

Removes the primer from the lagging strand and replaces it with DNA (Move in the 5’ to 3’ direction & have exonuclease activity which has a role in DNA repair)

Biology (64 decks)

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