CP 11 DNA Structure / Replication

Question 1

what is Griffiths experiment

Answer 1

Substance derived from killed infective pneumonia bacteria could transform a non infective living pneumonia bacteria to the infective type

Question 2

what are the 2 strains in griffiths experiment

Answer 2

Smooth (S) = Virulent, causes pneumonia killing mice
Rough (R) = Nonvirulent = does not kill mive

Question 3

what are the steps to griffiths experiment+what happens to the mice

Answer 3

• Mice injected with live S cells (mice die)
• Mice injected with live R cells (mice live)
• Mice injected with heat-killed S cells (mice live)
• Mice injected with heat-killed S cells + live R cells (mice die)

Question 4

why did the mice die when mixing live R strain and killed S strain ?

Answer 4

Living R bacteria had acquired traits from dead S bacteria transformed into virulent S cells

Question 6

what does each nucleotide contain of

Answer 6

1 - 5 carbon sugar
1 phosphate grp
1 nitrogenous base

Question 7

what is chargaffs rule

Answer 7

Number of purines equals number of pyrimidines

Question 8

what are the purines and pyrimidines

Answer 8

pur = AG
pyr = TC

Question 9

TF polynucleotide chain does not have polarity

Answer 9

F, it does

Question 10

in the polynucleotide chain where does the phosphate and hydroxyl group bind

Answer 10

P = 5’ end
H = 3’ end

Question 11

how does x-ray diffraction work

Answer 11

• X-ray beam directed at molecule in form of regular solid (ideally a crystal)
• Positions of atoms in molecule deduced from diffraction, patterns produced on photographic film

Question 12

what is the basic structure of the double helix

Answer 12

Two polynucleotide chains (sugar phosphate backbones) twist around each other in right-handed way, pairs of bases fill the central space

Question 13

what are the 3 models of DNA replication

Answer 13

• Semiconservative
• Conservatice replication
• Dispersive replcation

Question 14

what are the steps to semiconservative replication

Answer 14

• Hydrogen bonds between two strands break
• Two strands unwind and separate
• Each strand acts as template for synthesis of new, complementary strand
• Each new double helix has one old strand (parental DNA) and one new strand

Question 15

what are the steps to conservative replication

Answer 15

• parental DNA strands unwind
• each is template for synthesis of new strand
• after replication, the 2 parental and 2 resulting strands pair up again
• resulting helicases are 2 old strands and 2 new strands

Question 16

what are the steps to dispersive replication

Answer 16

• double helix unwinds
• both strands of DNA are chopped up into pieces
• pieces are then replicated individually, in each piece, new DNA nucleotides pair with the old ones
• newly synthesized DNA fragments and the original DNA fragments are randomly interspersed and reassemble into two complete DNA molecules

Question 17

what does DNA polymerase use for DNA replication

Answer 17

4 dNTP’s (deoxyribonucleoside triphosphates)
dATP, dGTP, dCTP, dTTP

Question 18

which direction does DNA polymerase assemble nucleotide chains

Answer 18

5’–>3’ (daughter strand)

Question 19

which way it the DNA template read

Answer 19

3’–>5’ (parental strand)

Question 20

what is the structure of a DNA polymerase

Answer 20

• Hand shaped
• Template DNA lies over “palm” in groove formed by “fingers” and “thumb”

Question 21

how do the DNA polymerase,3’-OH, new and template strand all work together

Answer 21

Template strand and 3′-OH of new strand meet at active site for DNA synthesis polymerization
reaction, located in palm domain

Question 22

what is the sliding DNA clamp

Answer 22

Protein that encircles DNA and attaches to rear of DNA polymerase, Tethers DNA polymerase to
template strand and increases rate of DNA synthesis

Question 23

What are Single-stranded binding proteins (SSBs) used for

Answer 23

Coat exposed single-stranded DNA segments
to Keep them from pairing

Question 24

what does Topoisomerase do

Answer 24

cuts and rejoins DNA to prevent twisting as DNA unwinds

Question 25

TF RNA primers replaced with DNA
later in replication

Answer 25

T

Question 26

Whats the difference between RNA polymerase 1 and 3

Answer 26

RNA 3 = Main polymerase
RNA 1 = removes RNA primer, replaces with
DNA on lagging strand

Question 27

whats the difference between DNA Ligase and DNA helicase

Answer 27

Ligase = binds fragments together
Helicase = unwinds Okazaki DNA

Question 28

what is an Okazaki Fragment

Answer 28

short pieces of DNA that are created on the lagging strand during DNA replication

Question 29

what is a replication bubble

Answer 29

Unwinding at an ori produces two replication forks, joined together to form replication bubble

Question 30

what are telomeres

Answer 30

caps that protect the end of eukaryotic chromos after the primer leaves

Question 31

what does telomerase do

Answer 31

Counteracts shortening of telomeres,
Adds telomere repeats to chromosome ends