There are two processes
• Transcription-Copying of DNA code to
• Translation-Conversion of RNA code into a
sequence of amino acids.
Transcription-RNA polymerase binds to double helix at
DNA DOUBLE HELIX
Bonds between bases are broken and DNA double helix unwinds
Free nucleotides from inside nucleus bind onto exposed DNA
bases forming a molecule of mRNA
When mRNA has formed, it moves away and the DNA reforms
+ DNA double helix rewinds
•The 5` end of the polynucleotide mRNA is modified by a
guanine cap which is thought to be a translation promoter.
•About 100 adenines (POLY A) are added to the 3` end
which is thought to:
>to be a signal for the exit of mRNA from the nucleus.
>Protect mRNA from enzyme action.
Translation- Diagram of an anti-codon
Anti Codon bases
2 codons enter the information processing region of ribosome.
An anti-codon attaches to the bottom of ribosome and codes the
amino acid with corresponding bases.
A second anti-codon comes along and after it has coded
its amino acid, a peptide bond is formed between the 2
The first anti-codon detaches leaving its amino acid behind.
The mRNA moves along ribosome and a third tRNA binds onto the
2nd and 3rd codons
By Sahira, Kulsoom and Sarah.