DNA and its roll in heredity

Question 1

bases of DNA

Answer 1

purines: adenine (A), guanine (G)
pyrimidines: cytosine (C), thymine (T)

Question 2

DNA

Answer 2

polymer of nucleotides

Question 3

Chargaff’s rule

Answer 3

the amount of purines is always equal to the amount of pyrimidines

Question 4

Rosalind Franklin

Answer 4

-prepared crystallographs from DNA samples
-Rosalind’s data aided the discovery of the double helical structure of DNA

Question 5

x-ray diffraction data indicated that…

Answer 5

• The bases are on the inside of each strand
• The sugar-phosphate groups are on the outside of each strand
• The chains run in opposite directions-antiparallel

Question 6

possible replication patterns

Answer 6

-semiconservative
-conservative
-dispersive

Question 7

semiconservative

Answer 7

Each parent strand is a template; New molecules have one old and one new strand

Question 8

conservative

Question 9

dispersive

Answer 9

DNA fragments are templates, old and new pieces are assembled into new molecules

Question 10

semiconservative replication

Answer 10

-the correct model

Question 11

3 steps in DNA replication
(in S phase)

Answer 11

-initiation
-elongation
-termination

Question 12

origin of replication

Answer 12

-large protein complex binds
-where DNA replication starts

Question 13

replication forks

Answer 13

-DNA is unwound and replication proceeds in both directions
-the open area of DNA where replication can take place

Question 14

DNA helicase

Answer 14

uses energy from ATP hydrolysis to unwind DNA

Question 15

single-strand binding proteins

Answer 15

prevents strands from re-binding

Question 16

DNA polymerase

Answer 16

-how new DNA is made
-require a template and primer
-can only add nucleotides to a pre-existing strand

Question 17

DNA primase

Answer 17

-makes the required primer
-a short starter strand of RNA
-DNA polymerase can build onto

Question 18

DNA ligase

Answer 18

-links DNA fragments (Okazaki strands)
-catalyzes final phosphodiester linkage between fragments
-fills gaps

Question 19

leading strand

Answer 19

grows at the 3’ end as the fork opens

Question 20

lagging strand

Answer 20

the exposed 3’ end gets farther from the form and an unreplicated gap forms

Question 21

Okazaki fragments
(DNA fragments)

Answer 21

small, discontinuous stretches where the synthesis of the lagging strand occurs

Question 22

telomeres

Answer 22

repetitive sequences at the end of eukaryote chromosomes

Question 23

telomerase

Answer 23

catalyzes addition of lost telomeres

Question 24

proofreading repair

Answer 24

-DNA polymerase recognizes mismatched pairs and removes incorrectly paired bases
-catches 99% or more mismatches

Question 25

mismatch repair

Answer 25

newly replicated DNA is scanned for mistakes by other proteins and mismatches can be corrected

Question 26

excision repair

Answer 26

enzymes scan DNA for damaged bases-they are excised and DNA polymerase 1 adds the correct ones