DNA structure and replication

Question 1

ribose + phosphate = what sort of bond

Answer 1

phosphodiester

Question 2

ribose + nitrogenous base= what sort of bond

Answer 2

glycosidic

Question 3

name the purines and describe them

Answer 3

G and A hexagon plus pentagon

Question 4

name the purines and describe them

Answer 4

G and A hexagon plus pentagon

Question 5

how many H bonds exist in an A - T base pair?

Answer 5

2

Question 6

what is the difference between C and U

Answer 6

U is deaminated C

Question 7

what is the difference between U and T

Answer 7

T is methylated U

Question 8

what makes up a nucleosome?

Answer 8

8 histones + 146 base pairs

Question 9

Name the enzyme that unwinds DNA for replication

Answer 9

gyrase

Question 10

what happens after gyrase has gyrated?

Answer 10

Helicase breaks the H bonds between base pairs

Question 11

after Helicase has split the DNA chain, what happens next?

Answer 11

free floating activated nucleotides in the cytoplasm pair up

Question 12

which enzyme tells DNA polymerase to start binding?

Answer 12

Primase

Question 13

What does DNA polymerase do?

Answer 13

Joins the new sugar-phosphate backbone together with covalent bonds

Question 14

Where do you find Okazaki fragments

Answer 14

lagging strand

Question 15

what joins the Okazaki fragments together?

Answer 15

ligase

Question 16

what’s the difference between eukaryotic and prokaryotic DNA replication

Answer 16

E: loads of (simultaneous) origins of replication
P: only one origin of replication

Question 17

what is a topoisomerase

Answer 17

enzyme that prevents supercoiling

Question 18

what is a quinolone

Answer 18

antibiotic for urinary and resp infections. interferes with topoisomerases leading to supercoiling in bacterial replication

Question 19

what is trimethoprim

Answer 19

antibiotic used for urinary tract infections. Interferes with nucleotide synthesis

Question 20

what else does DNA polymerase do?

Answer 20

proofreading and editing DNA replication

Question 21

what’s the smallest sort of DNA repair?

Answer 21

Base excision repair

Question 22

describe Base Excision Repair

Answer 22

single incorrect base is removed (eg U instead of C), DNA polymerase adds correct base, DNA ligase seals the nick

Question 23

What is the other single strand repair system other than base excision repair

Answer 23

Nucleotide excision repair

Question 24

when do you get nucleotide excision repair and what happens?

Answer 24

when you get a dimer on one strand. DNA helicase chops out o 12 nucleotide gap in one strand. DNA polymerase and ligase fix it

Question 25

What are Mut S and Mut L

Answer 25

enzymes responsible for fixing DNA mismatches. Mut S binds to the mismatched base pair and MutL scans for a mysteriously made NICK nearby and chops out a lump of DNA up to the mismatch

Question 26

what’s the best way of dealing with a double strand break?

Answer 26

homologous recombination. DNA sequence is copied from the sister chromosome.

Question 27

name a disease with defective homologous recombination pathway

Answer 27

BRCA2 breast cancer

Question 28

name a disease wherein mutS and mutL don’t work properly

Answer 28

colon cancer

Question 29

name a disease linked to nucleotide excision repair defects

Answer 29

Xeroderma Pigmentosum