L9 - Protein Synthesis I

L9 – Protein Synthesis I: DNA Transcription


Slide 4 – DNA as genetic information

• 1944 – Avery: DNA as genetic material
• 1953 – Crick and Watson: DNA structure
• 1957 – Crick: The central dogma


Slide 5 – The central dogma of molecular biology

• “Once information has got into a protein it can’t get out again”




Slide 6-7 – Coding properties of nucleic acids

• Three key sets of experiments defined relationship between nuclear DNA and protein
expression
- A messenger exists that transmits information from the nucleus to the cytoplasm
(Brenner, 1960)
- The genetic code is read in triplets (Crick 1961, Nirenberg 1961, Khorana 1960s)
- The amino acid sequence is linearly related to the DNA sequence (Yanofsky, 1967)


Slide 8 – Transcription: from RNA to DNA

• When you make an RNA molecule, you read it from the template strand and make a
copy of it, which is then the same sequence with the upper (coding) strand
- Except for uracil in RNA and missing oxygen in DNA

, Slide 9 – RNA structure




Slide 10-11 – Transcription: RNA synthesis

• RNA polymerase enzymes make RNA
• Addition of nucleotides in 5’ to 3’ direction
• Requires a template, two strands of DNA need to be separated