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BIMM 120 > Bacterial replication, transcription, translation > Flashcards

Bacterial replication, transcription, translation Flashcards

1
Q

Prokaryotic genomes

A

They have fewer chromosomes than eukaryotes and are usually circular

they also include plasmids - which are much smaller than chromosomes

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2
Q

what is the size of human chromosomes

A

47,000-250,000 kb (47-250 million bp)

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3
Q

How do prokaryotic genomes fit in the cell?

A

supercoiling

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4
Q

What is supercoiling?

A

main circular chromosomes

They wrap the DNA around histone-like proteins, and twists the DNA to be compact with the help of Topoisomerase II and I

negative supercoiling compacts the genome another 100x

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5
Q

What does Topoisomerase II do?

A

makes a negative supercoil
and it cuts double strand of DNA helix and then reseals them

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6
Q

What does Topoisomerase I do?

A

it makes a positive superocoil and converts the DNA back to its original state

it cuts a single strand of the DNA helix and reseals the break, this helps relieve tension

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7
Q

what is monocistronic

A

one promoter encodes one gene

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8
Q

what is polycistronic

A

one promoter encodes multiple genes

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9
Q

what are the steps of bacterial replication

A
  1. when the cell is ready for replication a replication initiation factor (DnaA) binds to the origin and a replication bubble opens
  2. then the helicase unwinds DNA and the single stranded DNA-binding proteins (ssDNA-binding proteins) bind to the DNA. replication forks progress in opposite directions. gyrase releases supercoil
  3. then DNA polymerase III extends the primers and the replication forks progress in opposite directions
  4. Leading and lagging strands form and DNA polymerase III has proof reading capacity
  5. DNA polymerase I removes primers and replaces them with DNA

Ligase repairs the nicks

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10
Q

how many origins and terminus are there in a bacterial chromosomes

A

one origin and one terminus

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11
Q

What is gyrase and what does it do?

A

Gyrase (topoisomerase) cuts the DNA strands and allow it to free rotate

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12
Q

where does replication take place in prokaryotes vs eukaryotes?

A

replication occurs in the cytoplasm for prokaryotes

and it occurs in the nucleus for eukaryotes

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13
Q

What is catenane?

A

a unique problem for circular genomes where DNA replication results in a catenane of linked rings

this is where topoisomerase comes into play
it breaks and re-joins the strands resolving the link

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14
Q

what are plasmids and what are the advantages?

A

they are always circular and are much smaller than bacterial chromosomes

they arent normally required by the cell but they can have some advantages like

  • antibiotic resistance
  • synthesis of antibiotics
  • nitrogen fixation
  • resistance to toxic metals
  • pathogenesis
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15
Q

how do plasmids replicate?

A

they replicate independently from chromosomes and it is happening all the time

they do rolling circle replication, Rep A binds to a section of the plasmid’s double stranded DNA by nicking one of the strands and hold on to the 5’ prime end to allow 3’ prime end to act as a host for DNA polymerase and then it recruits a helicase to unwind the DNA and it becomes a single strand the two ends of the nick strand are rejoined by the rep A and the DNA ligase seals the nick in the single strand

the single strand DNA can now be replicated and the region of DNA becomes looped allowing RNA polymerase access to the DNA to form a primer and host DNA polymerase uses the primer as a synthesis of DNA

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16
Q

why is having low levels of plasmid a disadvantage

A

because if the cell divides then you may be left with a daughter cell that did not receive the plasmid

17
Q

what is the structure of bacteria genes and when are they functional?

A

promoter –> RBS (ribosome binding site) –> ATG –> coding –> stop codon –> terminator

during transcription only the promoter and terminator are functional (RNA polymerase reads the terminator as the ending signal and the promoter as the beginning signal)

during translation only the RBS, ATG, coding, and stop codon are functional

18
Q

when does transcription start?

A

After the promoter (+1)

19
Q

What does RNA polymerases do?

A

It carries out transcription y making RNA transcripts from DNA template strands

20
Q

What are sigma factors and where do they bind?

A

they direct RNA polymerase to specific promoters

sigma factors bind to
-10 element
-35 element

21
Q

what are the phases that don’t change?

A

conserve, you can take the most conserve nucleotides and make a consensus sequence

22
Q

what are the stages of transcription?

A

3 stages

  1. Initiation
    - RNA polymerase holoenyzme binds DNA and scans for promoter
  2. elongation
    - sigma factor falls off, and the RNA is extended within a transcription bubble, gyrase relaxes the supercoiling caused by unzipping the DNA
  3. termination
    - RNA polymerase and the transcript fall off
23
Q

Which is the complimentary stand and which is the template strand during transcription

A

the top strand is complimentary and the bottom is the template strand

mRNA is made using the lower strand as a template

24
Q

what are the types of RNA?

A
  1. mRNA (messenger RNA)
  2. rRNA (ribosomal RNA)
  3. tRNA (transfer RNA)
25
Q

what do mRNA do?

A

they encode proteins and this all happens in the cytoplasm

26
Q

what do rRNAs do?

A

they form ribosomes and is catalytic (structural, does not get translated, is apart of ribosome)

ribosomes are made up of proteins and RNA and they have no membrane

27
Q

what is ribozyme?

A

a peptidyltransferase that catalyzes a reaction

a catalytic RNA

28
Q

what do tRNA do?

A

they shuttle amino acids for translation
they are each bond to an amino acid and they bring it to the RBS

they have an anticodon loop and acceptor end

29
Q

what are the steps for bacterial translation?

A
  1. Ribosome binds to RBS
  2. Amino acids are brought by tRNA and fMet
  3. Translation stop when the stop codon shows up
30
Q

What occurs simultaneously at the same time?

A

Transcription and translation because there is no nucleus separating them

once transcription ends the 5’ end of the RNA comes off and the ribosome jumps on the RBS and it reads the RNA 5’ to 3’

BIMM 120 (26 decks)

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