1. Protein and Translation

2. Central Dogma of Biology _____________________________________: -Transcription: The decoding of DNA into mRNA -Translation: The decoding of an mRNA message into a polypeptide chain

3. Proteins Proteins are made of: ____________________ A few ___________ joined together are called polypeptide chain: -Each poly peptide contains a combination of any or all of the 20 different amino acids -The property of the protein is determined by the order of the amino acids

4. Translation The “language” of the mRNA instruction is called the genetic code How can a code with just 4 letter (A,U,C,G) carry instruction for 20 amino acid? -The genetic code is read 3 letters at a time -Eg. UCGCACGGU This sequence would be read 3 bases at a time: UCG-CAC-GGU

5. Translation Each 3 letter “word” in mRNA is know as a codon: -A codon consist of 3 consecutive nucleotides that specify a single amino acid -eg. Using codons, the sequence UCG-CAC-GGU would be translated into: Serine – Histidine – Glysine

7. Problems Transcribe the following DNA sequence into mRNA: T A C A A G G G T C A C A T C Translate the above mRNA into protein:

8. Codons Some amino acids can be specified by more than one codon e.g. 6 different codons specify the amino acid leucine One codon can only code for one amino acid e.g. the codon CAG can only code for the amino acid Glutamine The codon AUG, code for ____________, serves as the start codon There are 3 “Stop” codon that do not code for any amino acid

9. Ribosome Before transformation can occur, mRNA must be transcribed from DNA in the nucleus and released into the cytoplasm Translation happens in the ribosomes in the cytoplasm

10. tRNA tRNA: transporting specific amino acid to the ribosome to be added on the growing polypeptide chain Each tRNA has: -An amino acid attach to one end -A region of 3 unpaired bases at the other end (anticodon): the bases on the anticodon are complementary to the mRNA codons E.g. the anticodon base for AUG would be UAC

11. Translation The ribosome joins the two amino acids on the two adjacent tRNA and moves along the mRNA binding more amino acids to the peptide chain