E7 Translation and protein synthesis Flashcards

1
Q

what is a gene?

A
  • a section of DNA that directs the synthesis of one or more overlapping mature RNA molecules (including parts of DNA that are not transcribed themselves but are necessary for transcription)
  • genes can overlap with each other
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2
Q

describe how tRNA, mRNA and rRNA are involved in translation

A

mRNA contains the code
- need a start and stop codon within the mRNA strand

tRNA is the decoder
- brings the correct amino acid to the correct codon using complementary base pairing

rRNA links the amino acids in the polypeptide

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3
Q

what does the ribosome do at the start of translation?

A
  • scans for ATG start codon
  • starts translation there
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4
Q

which direction does a ribosome translate mRNA in?

A

5’ to 3’

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5
Q

contrast ribosomes in eukaryotes and prokaryotes size-wise

A

eukaryotes = 80S
60S and 40S subunits

prokaryotes = 70S
50S and 30S subunits

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6
Q

what are the 3 main steps of protein synthesis?

A
  • initiation
  • elongation
  • termination
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7
Q

describe initiation as a step of protein synthesis

A
  • finding the start codon (ATG) and assembling the ribosome with the first tRNAs
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8
Q

describe elongation as a step of protein synthesis

A
  • aminoacyl tRNA binding (codon recognition)
  • peptidyl transfer (peptide bond formation, mediated by ribosome)
  • translocation (moving to next codon)
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9
Q

describe aminoacyl tRNA binding in translation elongation

A
  • codon is read
  • correct tRNA binds
  • tRNA-mRNA base pairing (between codon and anticodon) is recognised by the ribosome and shifts along by a conformational change
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10
Q

describe peptidyl transfer in translation elongation

A
  • catalysed by the ribosomal RNA
  • amino acid is added and polypeptide is elongated
  • allows old tRNA molecule (without amino acid) to detach and have a new amino acid attached
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11
Q

describe translocation in translation elongation

A
  • ribosome changes conformation
  • mRNA and tRNAs have moved by one codon relative to the ribosome (ribosome is ready for next aminoacyl-tRNA and doesn’t interact with the old one)
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12
Q

describe the termination step of translation

A
  • no tRNA molecule binds to a stop codon
  • tRNA shaped protein called a release factor recognises stop codon
  • peptidyl-tRNA bond is hydrolysed
  • release factors and protein are released
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13
Q

what concept allows for the targeting of prokaryotic ribosomes by antibiotics?

A
  • the differences between eukaryotic and prokaryotic ribosomes
  • different RNAs, different subunits
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14
Q

how do antibiotics typically work?

A
  • prevent translation by preventing elongation
  • inhibits the main enzyme for replication and growth
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15
Q

state the 4 basic synthetic genetic processes

A
  • replication
  • transcription
  • RNA processing
  • translation
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16
Q

describe RNA processing as a synthetic genetic process

A
  • ‘splicing’, capping, polyadenylation
  • modification of RNA in the nucleus and possibly later in the cytoplasm
  • removing sections of mRNA that aren’t needed for translation of the mRNA strand