Transcription:

• DNA is ‘unzipped’ by DNA helicase and this breaks the hydrogen bonds between the complementary bases

• Free nucleotides line up along the anti-sense strand

• RNA polymerase catalyses the phosphodiester bonds being formed between adjacent nucleotides

• The mRNA moves out of the nucleus from the nuclear pore into the cytoplasm

  RNA vs DNA:

• RNA is smaller and DNA is larger

• RNA has uracil instead of thymine in DNA

• RNA is single stranded and DNA is double stranded

  Transcription vs replication

• Replication uses both strands and transcription only uses one strand

• Replication forms DNA and transcription forms mRNA

• Replication uses DNA polymerase and transcription uses RNA polymerase

• Replications’ product stays in the nucleus and transcriptions product leaves the nucleus

  Translation****:

• The ribosome attaches itself onto the mRNA strand

• Ribosome slides along until the start codon (AUG) is reached

• A tRNA molecule binds to the mRNA via its anti-codon and forms hydrogen bonds - the tRNA molecule is attached to a specific amino acid

• The next tRNA molecule brings another amino acid and binds to the next codon - the amino acids form peptide bonds in between them

• This process repeats until the stop codon or release factor is reached on the mRNA

  DNA replication

• DNA is ‘unzipped’ by DNA helicase

• The hydrogen bonds are broken between the bases

• The strands act as templates to the new strand

• The exposed bases attract complementary bases

• They form new hydrogen bonds between them And adjacent nucleotides are joined by phosphodiester bonds formed in condensation reactions

• DNA polymerase and DNA ligase form the sugar-phosphate backbone

• 2 identical DNA strands are formed

• This happens semi-conservitavly (one strand is old, one strand is new)