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Genetics > Prokaryote Genetics > Flashcards

Prokaryote Genetics Flashcards

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1
Q

where does transcription occur?

A

in the cytoplasm

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2
Q

how does it differ from eukaryote genetics?

A

no separation of DNA, transcription and translation are coupled

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3
Q

how does prokaryote translation timing differ in prokaryotes?

A

translation begins when the mRNA is still being synthesised

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4
Q

what is the order of a prokaryote gene?

A

promoter, transcription start site, RNA coding sequence, termination site and terminator gene

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5
Q

how is the DNA packaged?

A

one or more circular chromosomes and plasmids

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6
Q

how is the DNA coiled?

A

circular chromosomal DNA coiled into looped domains and then further supercoiled into looped DNA

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7
Q

what is the leading strand replicated with?

A

DNA polymerase III

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8
Q

what is the lagging strand replicated with?

A

DNA polymerase I

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9
Q

what is another function of DNA polymerase I?

A

removes the RNA primer from the DNA strand

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10
Q

what does topoisomerase 4 do?

A

disconnects the 2 strands

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11
Q

why are repressor proteins needed?

A

as genes are usually switched on by default

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12
Q

what promotor elements are on prokaryote genes?

A

-35 and -10 promotor sections

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13
Q

what are promotor sections?

A

parts of the DNA that the polymerase directly binds to

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14
Q

what is a pribnow box?

A

-10 element

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15
Q

what enzyme is used for transcription?

A

RNA polymerase

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16
Q

what is a holoenzyme?

A

a compound formed by the combination of an enzyme and its coenzyme

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17
Q

what is RNA polymerase made up of?

A

5 subunits and a sigma factor

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18
Q

how is an open complex formed?

A

the sigma factor binds to the -10 and -35 promotor elements which forms a transcription bubble

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19
Q

how is the bubble able to continue down the strand?

A

when a short mRNA strand is produced, the sigma factor is released

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20
Q

what are the two types of stop signals?

A

rho-independent and rho-dependant

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21
Q

how does rho-independent signals work?

A

hairpin loop in the DNA is formed which is followed by U bases causing a weaker bond between the U and the A bases so the strand dissociates

22
Q

how is the hairpin loop formed?

A

signal region contains a section that is repeated a few bps away in the inverted sequence, followed by U bases

23
Q

how does rho-dependant signals work?

A

rho factor binds to the end of the mRNA chain and catches up to the RNA polymerase, knocking it off via the torpedo effect

24
Q

what are the things needed for prokaryotic translation?

A

mRNA strand, ribosomes, initiation factors, tRNA

25
Q

what ribosomes are used in prokaryotes?

A

70s, with 50s and 30s subunits

26
Q

where and why does the ribosome bind to the DNA?

A

binds at the shine-delgarno sequence, due to a portion of the 16s rRNA on the small subunit being complementary

27
Q

what promotes the binding of the 16s rRNA?

A

IF3

28
Q

how does the initiator tRNA then bind to the strand?

A

IF2 promotes the binding of the tRNA to the mRNA strand

29
Q

what is the final step in attachment?

A

IF2 and IF3 are released and the 50s subunit attaches

30
Q

how does elongation occur?

A

tRNA binds to the complementary codon, then the next anticodon binds at the entry site causing a peptide bond to form, and the ribosome moves along the strand

31
Q

what are the 3 different release factors?

A

RF1 and RF2 and RF3

32
Q

how do prokaryotes control gene expression?

A

genes grouped together in operons which are controlled using a single promotor region

33
Q

how might operons be inhibited?

A

repressor can bind to an operator region to physically block the movement of polymerase

34
Q

how might operons be activated?

A

activators can bind next to the DNA polymerase and increase the rate of translation

35
Q

what is an inducible operon?

A

operons that are usually switched off and can be switched on by an inducer

36
Q

what is a repressible operon?

A

operons that are usually switched on and can be switched off using a corepressor

37
Q

what does the lacZ gene code for?

A

beta galactosidease

38
Q

what does lacY gene code for?

A

beta galactosidase permease

39
Q

what does the lacA gene code for?

A

beta galactosidase transacetylase

40
Q

what does the lacI gene code for?

A

lactose repressor

41
Q

what does beta galactosidase do?

A

converts lactose to glucose and galactose

42
Q

what does beta galactosidase permease do?

A

membrane bound protein that pumps lactose into a cell

43
Q

what does beta galactosidase transacetylase do?

A

enzyme that transfers acetyl group from acetyl co-A to beta galactosides

44
Q

what does lactose repressor do?

A

represses expression of lactose metabolising genes

45
Q

what causes negative expression of lac operon?

A

absence of lactose represses expression

46
Q

what causes positive expression of the lac operon?

A

absence of glucose activates the expression

47
Q

how does the absence of lactose help the cell to save energy?

A

does not transcribe enzymes that do not need to be present

48
Q

how does the presence of lactose allow transcription?

A

allolactose binds to the repressor and stops it from preventing translation

49
Q

how does the absence of glucose activate transcription of the lac operon?

A

CAP and cAMP binds to the CAP binding site and facilities the binding of RNA polymerase

50
Q

what happens when there is no glucose and no lactose?

A

no transcription due to CAP being active and bound to the DNA and lac repressor acts as a roadblock

Genetics (8 decks)

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