12.3 KEY CONCEPT Translation converts an mRNA message into a protein. Occurs on ribosomes

Instruction to make proteins are on the mRNA strand. 12.3 Instruction to make proteins are on the mRNA strand. Translation converts mRNA messages into a polypeptide chains of amino acids which will eventually become a protein. Start codon- allows the process of translation to begin. AUG are the three letters Codons are a sequence of three nucleotides that codes for a specific amino acid. See pic below Stop codons- tells the process to stop. There are three stop codons: UAA,UAG,UGA codon for methionine (Met) leucine (Leu)

Ribosomes consist of two subunits. 12.3 Ribosomes Ribosomes are the site of translation. Can be free floating or on rough ER Ribosomes consist of two subunits. The large subunit has three binding sites for tRNA. The small subunit binds to mRNA.

The anticodon can attach to mRNA’s codons . 12.3 What gets the amino acids and links them together to become a protein? A tRNA molecule does! An anticodon is on the bottom of tRNA and is a set of three nucleotides that is complementary to an mRNA codon. The anticodon can attach to mRNA’s codons . A tRNA molecule retrieves the correct amino acids and brings it to the ribosome.

Process involved in Translation: 1. Initiation: 12.3 Process involved in Translation: 1. Initiation: a. mRNA enters the cytoplasm and attaches to -ribosome’s small subunit b. rRNA reads mRNA codon by codon c. once a start codon (AUG) is read, tRNA retrieves the specific amino acids and returns to ribosome. d. tRNA’s anticodons pair up with the mRNA codons through base pairing then can pop off amino acid and add to chain (complementary bases pair up A-U, G-C) 3. 4. 1.

12.3 2. Elongation: addition of amino acids one-by-one: Once the codons and anticodons are attached, the tRNA transfers its amino acid to the growing polypeptide chain, producing the protein - codon by codon! 2. 7. 5.

12.3 3. Termination: When rRNA reads a stop codon - UAA, UGA, or UAG – the process stops and the ribosome falls apart and the polypeptide chain of amino acids becomes a protein! 8. anticodons 6. Small subunit

Label the picture on your notes using the images from the last few slides!

How does translation relate to YOUR life How does translation relate to YOUR life? (Why do you need to know this, anyway?) All the proteins that make up YOU, your cells, your body, the foods you eat, all the living cells in the world, etc - are made this way! Every time your body needs more of a protein muscle protein, hair protein, enzymes, hormones, hemoglobin molecules,

Read the next two slides and we will go over in class tomorrow

Each codon represents an amino acid 12.3 Each codon represents an amino acid The genetic code matches each RNA codon with its amino acid or function. How to figure out what amino acid a codon codes for… 1. Find first letter of the codon in middle (use the biggest letters) 2. Moving outward find second letter of the codon 3. Continue moving outward to find third letter of the codon and corresponding amino acid

12.3 How one reads a frame can change the order in which the codons are arranged and change the resulting protein.