3.5 - Translation & Genetic Code Flashcards

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1
Q

Translation

A
  • Protein synthesis using RNA as template

- occurs outside of nucleus (unlike DNA replication and transcription)

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2
Q

RNA classes involved in translation

A

mRNA - encodes protein
rRNA - comprises machinery
tRNA - decoding adaptor

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3
Q

Prokaryotic ribosome components

A

Large ribosomal subunit: 23S rRNA + 5S + 31 proteins

Small ribosomal subunit:
16S rRNA + 21 proteins

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4
Q

Functional sites on the ribosome

A
  • Acyl site
  • Peptidyl site
  • Exit site
  • mRNA binding site (below P and A sites)
  • peptidyltransferase site
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5
Q

Transfer RNA

A
  • transport amino acids from the cytoplasm of a cell to a ribosome
  • at least 20 different tRNAs, one for each amino acid
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6
Q

Anticodon loop

A

-basepairs with codon on mRNA

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7
Q

Acceptor stem

A

-amino acid attachment site

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8
Q

Translation: Initiation

A
  • binds to Shine-Dalgarno sequence just before the start codon
  • Results in fully assembled ribosome w/ bound mRNA start codon under P and fmet-tRNA in the P site
  • includes: initiation factors (IF1, IF2, IF3), small & large ribosomal subunit, fmet-tRNA, mRNA (including Shine-Dalgarno sequence)
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9
Q

Translation: Elongation (of the polypeptide chain)

A
  • Amino acids are brought to the ribosome by tRNAs and linked together to form a chain
  • Acyl-tRNA binds to A site (amino acid attached), peptide bond forms between amino acids, translocation via GTP, new acyl-tRNA binds to A site, tRNA in E site leaves, new protein synthesized
  • includes: elongation factors (EF-Tu, EF-G, EF-Ts), acyl-tRNAs, ribosome, mRNA
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10
Q

Translation: Termination

A
  • Release factors required to cleave polypeptide from final tRNA
  • Dissociation of all components including completed polypeptide occurs
  • include: release factors (RF1, RF2, RF3)
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11
Q

Codons

A
  • 3 nucleotide long code words on mRNA that translate to amino acids by way of the tRNAs
  • AUG is start (met)
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12
Q

Redundancy of the genetic code

A

-More than one codon for a given amino acid (wobble)

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13
Q

Point mutations

A

-single base changes

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14
Q

Base substitutions: Synonymous

A
  • same amino acid

- no effect on function

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15
Q

Base substitutions: Missense conservative

A
  • similar amino acid

- may not effect function

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16
Q

Base substitutions: Missense nonconservative

A
  • dissimilar amino acid

- may alter function

17
Q

Base substitutions: Nonsense

A
  • stop codon

- destroys function

18
Q

Indels: frameshift

A
  • addition of nt
  • new polypeptide
  • alters function