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BIOL 207 > 3-1 > Flashcards

3-1 Flashcards

1
Q

DNA replication needs to be

A

Accurate and fast

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2
Q

Complementary bases suggest that each strand of a double helix could serve as

A

A template

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3
Q

Three proposed models of DNA replication

A

Conservative replication

Dispersive replication

Semiconservative replication

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4
Q

Conservative replication

A

Two original strands stay together in one molecule (double helix)

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5
Q

Dispersive replication

A

Each strand gets broken down, copied, and then reassembled

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6
Q

Semi-conservative

A

Each strand serves as a template, is copied, and each strand stays intact but two strands do not come back together

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7
Q

All DNA takes places in a

A

Semiconservative manner

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8
Q

Meselson and Stahl’s experiment

A

Creates an intermediate band of DNA between N14 and N15 after one round of replication to rule out conservative replication

Creates a intermediate band and a light band after a second round of replication to rule out dispersive replication

Agrees with semi-conservative replication

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9
Q

Major steps in DNA replication

A

Initiation

Unwinding

Elongation

Termination

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10
Q

Initiation

A

Prokaryotes have circular DNA with an OriC

OriC is recognized by initiator proteins, slightly unwinding DNA at the Ori

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11
Q

Unwinding

A

Stretch of DNA unwinds

Helicase and other single stranded binding proteins attach to single stranded DNA

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12
Q

Unwinding

Dna replication requires

A

Single stranded DNA

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13
Q

Unwinding

DNA Helicase needs

A

Single stranded DNA to do its job

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14
Q

Unwinding

DNA helicase

A

Breaks hydrogen bonds

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15
Q

Unwinding

Single stranded binding proteins

A

Protect single stranded DNA

Prevents secondary DNA structures

Sequence independent

Form tetramers

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16
Q

Unwinding

DNA gyrase

A

Topoisomerase (type II)

Relieves torsion by cutting DNA (dsDNA break)

Removes a twist via ATP

Reseals broken DNA ends

17
Q

Elongation

DNA polymerase

A

Synthesizes DNA strands

18
Q

Elongation

DNA polymerase can only attach nucleotides to a pre-existing

A

3’ OH group

19
Q

Elongation

Synthesized using

A

dNTP

20
Q

Elongation

DNA and RNA synthesis occurs in the

A

5’–>3’ direction

21
Q

Elongation

DNA polymerase 1,3 used in

A

Replication

22
Q

Elongation

Primers synthesis

A

Primase (a RNA polymerase) makes RNA primers

Joins with helicase at replication fork

23
Q

Elongation

DNA polymerase III

A

Synthesizes DNA from 5’ to3’ direction

Attaches new nucleotides to 3’ OH sugar phosphate backbone

Has 3’ to 5’ exonuclease activity (corrects errors)

24
Q

Elongation

Leading strand

A

Being synthesized towards the fork

One continuous DNA strand

5’ to 3’

25
Q

Elongation

Lagging strand

A

DNA synthesized away from fork

Discontinuous DNA strands called Okazaki fragment

5’ to 3’

26
Q

Elongation

DNA polymerase 1

A

Synthesizes DNA strand in 5’ to 3’ direction

Also has 3’ to 5’ and 5’ to 3’ exonuclease activity

Removes RNA primers and replaces them with DNA

Only on lagging strand

27
Q

Elongation

DNA ligase

A

After replacement by DNA poly 1, a gap still remains which is filled by DNA ligase

Joins Okazaki Fragments together

28
Q

Termination

A

DNA replication ends when two replication forks meet

Additionally, some organisms contain specific termination sequence (Ter) that stops DNA replication

29
Q

How is DNA replication accuracy achieved

A

Low error in base pair selection by DNA polymerase

Proofreading by DNA polymerase

Mismatch repair occurs soon after DNA replication

30
Q

Mismatch repair system

A

Abnormalities in DNA secondary structures recognized by mismatch repair system

Gets rid of nucleotides on new DNA strand

BIOL 207 (31 decks)

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