Chapter 13

Question 1

What year was it known that chromosome consisted of DNA and proteins?

Answer 1

1920s

Question 2

What crucial piece helped see the structure of Dna?

Answer 2

x -ray crystallography by rosalind franklin

results showed a spiral model}

Question 3

DNA is a polymer of nucleotides:

Answer 3

deoxyribose, a phosphate group, and a nitrogen containing base

Question 4

The bases:

Answer 4

Purines: Adenine and guanine
Pyrimidines: cytosine and thymine

Question 5

Erwin Chargaff found what is 1950?

Answer 5

A=T
C=G
this is chargaffs rule

Question 6

What is the dna structure?

Answer 6

Helical and antiparallel

Question 7

what happened in 1953?

Answer 7

watson and crick established the general structure of DNA

Question 8

What is the model of DNA?

Answer 8

double helix 
right handed
antiparallel 
-outer edges of nitrogenous bases are exposed in the major and minor grooves 
- complementary base pairings

Question 9

what is the direction of the strand determined by?

Answer 9

sugar - phosphate bonds

Question 10

what is the function of DNA?

Answer 10

4 important functions:

1. stores information
2. susceptible to mutation
3. precisely replicated
4. expressed as a phenotype

Question 11

What is the dna replication pattern?

Answer 11

semiconservative

Question 12

what are the two steps of DNA replication?

Answer 12

1. double helix is unwound, making two strands

2. new nucleotides are added to the new strand at the 3’ end and joined by phosphodiester linkages.

Question 13

how is the sequence determined?

Answer 13

complementary base pairings

Question 14

How does DNA replication begin?

Answer 14

with a short primer that is complementary to DNA template

Question 15

What is the primer called?

Answer 15

Primase- it synthesizes DNA one nucleotide at a time

Question 16

DNA polymerase III does what?

Answer 16

adds nucleotides to the 3’ end.

Question 17

what is Dna polymers shaped like?

Answer 17

open right hand palm. It brings the active site and the substrates into contact.

Question 18

what is the function of helicase?

Answer 18

uses energy from ATP hydrolysis to unzip the DNA

Question 19

what do SSBs do?

Answer 19

keep strands from connecting back together

Question 20

what is the replication fork?

Answer 20

the site where DNA unwinds to expose bases

Question 21

where does the leading strand extend?

Answer 21

toward fork

Question 22

where does lagging strand extend?

Answer 22

away from fork

Question 23

what are okazaki fragments?

Answer 23

synthesis of the lagoon strands that occur in small discontinuous stretches

Question 24

what three repair mechanism do cells have/

Answer 24

proofreading - as the DNA polymerase adds a nucleotide to a growing strand, it has a proofreading function - it the bases are paired incorrect, the nucleotide is removed
mismatch repair
excision repair

Question 25

what does ligase do?

Answer 25

fills in the gaps at the end in the lagging strand.

Question 26

what does polymerase III do?

Answer 26

adds nucleotides and extends

Question 27

what does polymerase I do?

Answer 27

replaced primer with DNA