PROTEIN SYNTHESIS

PRESENTATION

Adenine

Uracil

Guanine

Cytosine

There are two processes involved:

• Transcription-Copying of DNA code to form mRNA.

• Translation-Conversion of RNA code into a sequence of amino acids.

RNA POLYMERASE

DNA DOUBLE HELIX

Transcription-RNA polymerase binds to double helix at promoter region

Sense strand

Anti-sense strand

Bonds between bases are broken and DNA double helix unwinds

Sense strand

Anti-sense strand

Free nucleotides from inside nucleus bind onto exposed DNA bases forming a molecule of mRNA

Free Nucleotides

+ DNA double helix rewinds

mRNA

When mRNA has formed, it moves away and the DNA reforms

mRNA

5` end3` end

Guanine“CAP”

Poly-A

•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.

Anti Codon bases

tRNA

Amino acid

Translation- Diagram of an anti-codon

2 Codons

mRNA

Ribosome

5` end3` end

Anti Codon.

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.

mRNA

Ribosome

5` end3` end

Anti Codon.

A second anti-codon comes along and after it has coded its amino acid, a peptide bond is formed between the 2 amino acids

Peptide bond

5` end

3` end

Peptide bond

2nd and 3rd codons

The first anti-codon detaches leaving its amino acid behind.

The mRNA moves along ribosome and a third tRNA binds onto the third codon.

The EndBy Sahira, Kulsoom and Sarah.