Meriems lecture

Question 1

DNA replication is

Answer 1

semi conservative

Question 2

DNA replication in E.coli has 3 steps

Answer 2

1. Initiation, 2. elongation, 3. termination

Question 3

Elongation is performed by

Answer 3

DNA polymerase III

Question 4

The alpha subunit of RNApolII

Answer 4

is responsible for 5’ to 3’ polymerisation

Question 5

The epsilon subunit of RNApolII

Answer 5

is responsible for proof reading exonuclease, it removes any mismatches via a repair system

Question 6

To replicate the double helix,

Answer 6

the strands need to be separated, and this is an energy dependent process

Question 7

The DNA polymerase acts like a

Answer 7

hand (attach slide pic)

Question 8

DNA polymerase synthesises DNA strand in

Answer 8

5’ to 3’ direction

Question 9

The lagging strand cannot be replicated

Answer 9

continuously, the DNApolII will have to go backwards as the DNA continues to get unwound.

Question 10

The lagging strand forms a loop because

Answer 10

the DNApolII wants to move in the same direction

Question 11

The lagging strand forms a loop because

Answer 11

the DNApolII wants to move in the same direction

Question 12

RNA primers need to be removed

Answer 12

to complete replication

Question 13

DNA polI is responsible for

Answer 13

Maturation of Okazaki fragments (and DNA repair)

Question 14

Initiation of replication in E.coli occurs at

Answer 14

oriC

Question 15

SSB proteins bind to the separated strands to ensure

Answer 15

that both strands don’t re-ligate automatically

Question 16

SSB proteins bind to the separated strands to ensure

Answer 16

that both strands don’t re-ligate automatically

Question 17

H.Sapiens have

Answer 17

60000 origins of replication

Question 18

Eukaryotic DNA is assembled into

Answer 18

chromatin

Question 19

If there is a free double stranded end for DNA, this would suggest that

Answer 19

there has been some DNA damage

Question 20

End replication problem is basically where

Answer 20

the lagging strand will not completely replicate, resulting in a terminal gap

Question 21

Telomerase extends the 3’ end of

Answer 21

the chromosome. This means that overall, no genomic information has been lost from each time DNA replication occurs.

Question 22

Telomerase is activated in

Answer 22

85% of cancers

Question 23

DNA damage does not necessarily

Answer 23

mean mutation

Question 24

Rate of spontaneous mutations can be

Answer 24

5x10^-11 for mamallian systems

Question 25

Mutations can result from errors in DNA replication

Answer 25

1. failure of epsilon subunit of DNA polymerase to proof- read 2. Tautomeric shift of bases causing mismatches in base pairing

Question 26

Each of the 4 bases can exist in

Answer 26

alternative forms (tautomers)

Question 27

A tautomeric shift can cause a point mutation

Answer 27

Where a CG pair turns to a CG+, and causes the G+ to bind with T, and replication to thereby occur, it would result in a CG base pair to convert to a TA pair

Question 28

slippage of the template strand can cause

Answer 28

deletion

Question 29

Slippage on the newly synthesised strand can cause

Answer 29

insertion

Question 30

Mismatch repair system

Answer 30

repairs replication errors

Question 31

Base excision error

Answer 31

repairs damaged bases. This occurs via DNA glycosylase which removes the base and leaves a gap. AP endonuclease recognises a sugar with missing base and cuts the phosphodiester backbone of DNA. DNA polymerase I fills in the gap and DNA ligase seals the DNA strand

Question 32

Nucleotide excision repair

Answer 32

repairs unusual base structures which distort DNA such as pyrimidine dimers

Question 33

Mechanism of mismatch repair system

Answer 33

see attach slide

Question 34

What happens to your DNA upon DNA damage?

Answer 34

where there are two thymine bases beside each other, exposure to UV can cause Thymine dimers to form. This can be repaired using CPP photolyase and light. Placental mammals cant do this though so they just cut i.e. NER.

Question 35

Synthesis of RNA from DNA template require

Answer 35

RNA polymerase as well as RNTP's

Question 36

RNA polymerase copies one strand

Answer 36

of duplex DNA into RNA

Question 37

In prokaryotes, a single RNA polymerase

Answer 37

transcribes all genes

Question 38

The three steps of RNA transcription

Answer 38

1. initiation 2. elongation 3. termination

Question 39

Transcription is initiated at specific regions in DNA

Answer 39

- gene promoters

Question 40

There is a signal sequence on RNA which signals to end transcription

Answer 40

AAA

Question 41

Formation of charged tRNA

Answer 41

occurs via a synthetase enzyme joining amino acyl and tRNA

Question 42

tRNA's decode the

Answer 42

mRNA message

Question 43

Each amino acyl tRNA synthetase charges a tRNA

Answer 43

with the correct amino acid

Question 44

Translation also occurs in 3 steps

Answer 44

1. Initiation 2. Elongation 3. Termination

Question 45

Prokaryotes have

Answer 45

polycistronic mRNA's,

Question 46

Eukaryotes have

Answer 46

monocistronic mRNA's

Question 47

The initiator tRNA is the only tRNA which can

Answer 47

bind to the P- site

Question 48

Why regulate gene expression?

Answer 48

a) economical b) some gene products are required at different times or in different environments c) gene products are required in different amounts d) In eukaryotes, differential gene expression occurs during development

Question 49

How is gene expression regulated?

Answer 49

At the transcription level, initiation and elongation of the transcript At the post transcription level, Transcription processing (folding of mRNA prevents translation) and protein modification

Question 50

The E.coli sigma 70 sub unit recognises a specific set of gene promoters

Answer 50

and binds to the -35 and -10 regions

Question 51

The initiation of gene transcription is controlled by regulatory proteins

Answer 51

These include positive regulators and negative regulators. In prokaryotes, Activator proteins bind to a DNA sequence close to the promoter and help recruit the RNA polymerase to the promoter.

Question 52

Genes can be activated by either

Answer 52

binding the activator protein or removing the repressor protein

Question 53

Prokaryotes generally

Answer 53

have polycistronic mRNA's. This gene structure is called the operon.

Question 54

Lactose is the inducer of

Answer 54

the lac operon

Question 55

LacI creates the

Answer 55

lac repressor which binds to the operator to prevent transcription

Question 56

With no inducer present,

Answer 56

the repressor makes contact with the operator

Question 57

When inducer is present it binds

Answer 57

to repressor, altering its structure and it cannot bind to the operator

Question 58

The lac operon is positively regulated by

Answer 58

CAP

Question 59

Lactose + glucose =

Answer 59

low basal lac gene expression

Question 60

Lactose no glucose

Answer 60

high lac gene expression