Test 3: Ch. 16 DNA

Question 1

Three people discovered DNA

Answer 1

Watson, Crick, and Rosalind Franklin (1953)

Question 2

What did Rosalind do?

Answer 2

1) x-ray diffraction of DNA crystalize
2) hit crystal with x-rays
a) x-rays bent by electrons’ in DNA
b) diffracted x-rays expose photo film

Question 3

what did watson and crick do?

Answer 3

they interpreted the photograph

Question 4

What are the components of a DNA structure?

Answer 4

1) 5’ phosphate
2) deoxyribose sugar w/ free 3’ OH (hydroxyl)
3) bases (nitrogenous)
a) hydrophobic
b) Thymine Adenine
Cytosine Guanine
4) one DNA nucleotide
5) Phosphodiester bond
a) 5’ on a freee nucleotide attaches to the 3 OH’ on growing DNA strand
b) kick out water through condensation reaction
c) phosphodiester bond
6) double stranded (alpha helix)
a) anti parallel
b) 5’ and 3’ ends of two strands are side by side
c) each strand has a 5’ and 3’ end
i) 5’ phosho
ii) 3’ OH

Question 5

DNA structures: the bases are what?

Answer 5

NItrogenous

Question 6

DNA structure bases are hydrophobic or hydrophilic?

Answer 6

hydrophobic

Question 7

What are the pyridines and how many rings do they have?

Answer 7

thymine and cytosine

two rings

Question 8

what are the purines and how many rings do they have?

Answer 8

adenine and guanine

one hexagonal ring

Question 9

know how to draw a DNA nucleotide

Answer 9

3’ OH group
Base
5’ Phosphorous extends from #5 carbon

Question 10

know how to draw two DNA nucleotide.

Answer 10

they are connected by a phosphodiester bond

Question 11

what kind of bond are two DAN connected by?

Answer 11

phosphodiester bond

Question 12

5’ Phosphorous on a free nucleotide attaches to the what on growing DNA strand.

Answer 12

2’ OH

Question 13

what is kicked out during condensation reaction?

Answer 13

water

Question 14

in what direction do DNA strands replicate?

Answer 14

5’—> 3’ direction

Question 15

what happens before it starts to replicate?

Answer 15

unzips

Question 16

what happens when it is unzipping?

Answer 16

a) breaks bonds between bases
b) T and A are complementary and have two h-bonds connecting
c) C and G are complementary and have three h-bonds

Question 17

what is the direction that the replication goes called and what is that?

Answer 17

Bidirectional replication

a) both replicate 5’ –> 3’
b) but moving in opposite directions

Question 18

during the unwinding in DNA replication molecules, what happens?

Answer 18

1) DNA helicase
2) single strand binding proteins stabilize the unwound parts
3) replicon forms bubble and continues to enlarge by uncoiling in both directions

Question 19

what happens during the replication process and replication fork?

Answer 19

1) leading strand is replicated with direction of fork movement.
a) DNA polymerase III attaches DNA to the 3’ OH of RNA primer and starts to lay down nucleotides.
b) RNA primer 5-6 nucleotides placed in the middle of the replicon by primase
2) lagging strand replicates away from fork movement in the opposite direction
a) polymerase III synthesizes okazaki fragments (~1000 nucleotides) tagged by Primer I
b) 2nd okazaki bumps into primer I followed by primer two, and the DNA polymerase I cuts out the primer and fills in the gap with new DNA
c) new DNA replaces primer. gap left when DNA relocates primer b/t replacement DNA and okazaki 1. the gap is sewed up by DNA liagase

Question 20

when the new DNA replaces primer, what is the gap sewed up by?

Answer 20

DNA liagase

Question 21

tell me about chromosome packaging.

Answer 21

1) DNA winds around proteins called histones
2) DNA is negatively charged and histones are positive
3) 8 histones form a nucleosome over which DNA winds