4- biochem of nucleic acid

Question 1

what is central dogma?

Answer 1

it’s a theory to do with flow of information from DNA being transcribed to RNA then translated to protein

Question 2

what is a nucleoside?

Answer 2

base+sugar

Question 3

what is a nucleotide?

Answer 3

nucleoside + phosphate group

Question 4

what is nucleic acid made up of?

Answer 4

RNA = ribose (oxygen on carbon 2)
DNA = deoxyribose (no oxygen on carbon 2)

Question 5

which is longer out of purines and pyrimidines?

Answer 5

purines = longer
pyrimidines = shorter
(longer name= smaller molecule)

Question 6

what bases are purines?

Answer 6

adenine & guanine

Question 7

what bases are pyrimidines?

Answer 7

uracil, thymine and cytosine

Question 8

for base A what is:
a) name of base
b)name of nucleoside
c)name of nucleotide (for DNA & RNA)

Answer 8

a)adenine
b)adenosine
c)DNA = dATP (deoxy-adenosine-triphosphate) RNA + ATP

Question 9

for base T what is:
a) name of base
b)name of nucleoside
c)name of nucleotide (for DNA &RNA)

Answer 9

a)thymine
b)thymidine
c) dTTP = DNA
TTP = RNA

Question 10

for base C what is:
a) name of base
b)name of nucleoside
c)name of nucleotide (for DNA &RNA)

Answer 10

a) cytosine
b) cytodine
c) DNA = cCTP
RNA = CTP

Question 11

for base G what is:
a) name of base
b)name of nucleoside
c)name of nucleotide (for DNA &RNA)

Answer 11

a) guanine
b) guonosine
c) DNA = dGTP
RNA = GTP

Question 12

for base U what is:
a) name of base
b)name of nucleoside
c)name of nucleotide (for DNA &RNA)

Answer 12

a) uracil
b) uridine
c) dUTP
RNA = UTP

Question 13

what is the only end nucleotides are added to?

Answer 13

3’ end of growing strand

Question 14

what are nucelotides joined by?

Answer 14

phosphodiester bond

Question 15

what enzyme adds deoxyribonucleotides and then what happens in replication?

Answer 15

DNA polymerase adds next nucleotide at 3’ end of growing strand and releases a phosphate

Question 16

what is energy driving replication reaction?

Answer 16

when DNA polymerase adds nucleotide, pyrophosphate (2 phosphates joined) are released and the bond linking them is broken - releasing the energy to drive reaction

Question 17

what is a phospho-diester bond?

Answer 17

bond formed by phosphate on 5’ end of one nucleotide connected to hydroxyl on 3’ end of next nucleotide

Question 18

how do you know if RNA or DNA?

Answer 18

look at carbon 2 and if has oxygen then RNA and if no oxygen then DNA

Question 19

what are nucleotide analogues?

Answer 19

they’re nucleotides that prevent replication (terminate)
-they’re incorporated into growing viral DNA and lack 3’ OH group so chain elongation terminated

Question 20

why does nucleotide analogues as drugs work?

Answer 20

because viral reverse transcriptase has higher affinity of ZDV than human DNA polymerase (so instead of polymerase adding next nucleotide transcriptase wants ZDV)

Question 21

when must DNA be replicated in mitosis?

Answer 21

before division of daughter cells so they have complete complement

Question 22

how many origins of replication in a) eukayotes
b)bacteria

Answer 22

a) many
b) only 1 as smaller genomes

Question 23

what means replication finished in reasonable time?

Answer 23

replication starts simultaneously at several points in genome = bidirectionally (results in leading strand & lagging strand)

Question 24

when are replication forks created?

Answer 24

they’re formed at origins where DNA starts unwinding (simultaneously at each origin site) creating a space which is the repliciation fork

Question 25

which strand always had free 3’ end on daughter strand?

Answer 25

leading strand
(moves along 3’ to 5’ of DNA, adding nucleotides from 5’ to 3’ end of duaghter strand)

Question 26

what strand has okazaki fragments & what does it require ?

Answer 26

lagging strand is replicated in fragments since as DNA unwinds and 3’ end of DNA sequence exposed RNA primer binds and replicates up to it’s own 3’ end (towards DNA 5’ end) but it reaches end of loop and then DNA unwinds further so it starts back again at new unwound part with new primer. this means creating in okazaki fragments & multiple primers required which are joined by DNA ligase

Question 27

what synthesises primers?

Answer 27

primase

Question 28

what does DNA polymerase have to proof read and repair mistakes?

Answer 28

it has 3’ to 5’ exonuclease activity which removes incorrect nucleotide if detected (as if left in = mutation) and improves errors from every 10^4 to 10^10

->separate active site with exonuclease activity. The exonuclease activity allows the enzyme to remove incorrectly incorporated nucleotides

Question 29

what is needed to unwind helix for DNA replication?

Answer 29

helicase