Nucleic Acids to Proteins 3

Nucleic Acids to Proteins 3

Nucleic Acids to Proteins 3

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Reverse Transcription

  • Primer tRNA binds to a complementary primary binding site
  • A DNA sequence is synthesis (5' to 3')
  • The viral R and Ur regions at the 5' end are removed by reverse transcriptase H
  • The newly synthesised DNA segment makes a jump to the 3' end of the viral RNA and binds to the R region by base pairing
  • A long DNA sequence complementary to the viral RNA strand is then synthesised
  • The viral U3 and R regions are removed by reverse transcriptase H leaving the PP region
  • A complementary DNA sequence (5' to 3') is then synthesised
  • The tRNA primer is removed and second jump of the cDNA to the 3' end takes place
  • This is followed by the synthesis of a complementary DNA sequence
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Gemcitabine: Anticancer Nucleoside Analogue

  • Gemcitabine is used to treat various types of cancers such as pancreatic cancer, breast cancer, non-small cell lung cancer and bladder cancer
  • Gemcitabine has two active metabolites
    • gemcitabine diphosphate
    • gemcitabine triphosphate
  • The diphosphate inhibits ribonucleotide reductase, an enzyme that converts ribonucleotides into 2'-deoxyribonucleotides, inhibiting DNA synthesis
  • The triphosphate causes apoptosis through inhibition of DNA elongation
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Gemcitabine: Anticancer Nucleoside Analogue

  • Gemcitabine triphosphate takes part in DNA synthesis
  • Upon incorporation, it only allows the addition of one nucleotide after Gemcitabine, after which further DNA elongation is inhibited
  • Gemcitabine diphosphate binds irreversibly to the ribonucleotide reductase and inhibits its activity
  • This results in the inhibition of the synthesis of 2'-deoxyribonucleotides and so DNA synthesis is stopped
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