Translation Flashcards

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1
Q

what is translation?

A
  • RNA-directed synthesis of a polypeptide

- message in mRNA is interpreted by tRNA

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2
Q

where does tRNA get amino acids from? where does it transfer them to?

A

from the cytoplasm to the ribosome (location of polypeptide formation)

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3
Q

what are the three stages of translation?

A
  1. Initiation
  2. Elongation
  3. Termination
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4
Q

what happens during initiation stage of translation?

A

mRNA, tRNA with first amino acid (Met), and the two ribosomal subunits are all brought together to form initiation complex

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5
Q

how does initiation complex bind together? where does mRNA bind? where does tRNA bind, what does this establish?

A
  1. mRNA binds to the small ribosomal subunit near it’s 5’ end
  2. tRNA binds to start codon on mRNA
    - establishing reading frame
  3. Large ribosomal subunit binds to complex, completing Translation initiation complex
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6
Q

what happens during elongation stage? which direction does ribosome move along mRNA?

A
  • Amino acids are added one by one to polypeptide.

- moves along the mRNA from 5’ to 3’

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7
Q

what are the three steps in elongation cycle?

A

i. Codon Recognition
ii. Peptide Bond Formation
iii. Translocation
Ribosome moves down 3 bases
(one codon)

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8
Q

what happens during codon recognition step?

A
  • anticodon of incoming tRNA base-pairs with complementary mRNA codon in A site
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9
Q

what happens during peptide bond formation step?

A
  • Bond is formed between incoming amino acid and growing polypeptide chain (energy requiring)
  • Polypeptide chain transferred to tRNA in A site
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10
Q

what happens during translocation step?

A
  • Ribosome moves down 3 bases (one codon)
  • Empty tRNA released from E site (energy releasing)
  • tRNA with polypeptide chain moves into P site
  • Next codon to be translated moves into A site
  • Ribosome ready for next tRNA
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11
Q

how long does elongation stage continue for?

A

Steps are repeated until the STOP codon reaches A site

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12
Q

what happens during termination stage of translation?

A
  • Stop codon reaches the A site of the ribosome
  • Release Factor binds to the stop codon
  • Hydrolyses bond (adds water to bond) holding polypeptide to tRNA –> Completed polypeptide is released
  • Small and large subunits of ribosome separate and mRNA is released
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