Translation: RNA to Protein Objectives • Trace the path of protein synthesis. Review: One Gene One Polypeptide • DNA RNA Polypeptide • The DNA sequence for a gene is transcribed into a single-stranded RNA molecule. • The mRNA takes the message to the site of protein synthesis. Translation: From mRNA to Protein • Translation: The process of converting the information in mRNA into a sequence of amino acids in protein. • Translation occurs at the ribosomes. • Based on a three-base code. The Codon • Three-base sequence that codes for one amino acid. • 3 bases : 1 amino acid. Translating the Code • Read from the mRNA sequence. • AUG = Met (start) • GCG = Ala • UGA = stop • Translation requires transfer RNA (tRNA). Transfer RNA • tRNA translates the triplet code of mRNA into the amino sequence. • Anticodon: the three bases on tRNA that are complementary to the mRNA codon. • Carries a specific amino acid. Ribosomes • Site of translation • Coordinates the functioning of mRNA and tRNA. Translation Translation Translation Translation Translation 1. Describe what happens as the ribosome moves along the mRNA strand. Amino acids are added to the growing polypeptide chain until a stop codon is reached. Translation 2. What is the relationship between mRNA and the completed polypeptide? The sequence of codons in mRNA determines which amino acids compose the polypeptide and in what order. Translation Animations Simple Animation www.dnai.org animation Translation: A Review • Translation converts the mRNA code into the amino acid sequence of proteins. • Translation occurs at the ribosomes and uses tRNA. • tRNA carry specific amino acids and posses an anticodon which is complementary to the mRNA codon. Translation: A Review • At the ribosome, tRNA bring in their amino acids according to codon-anticodon pairing. • The amino acids bond together to form polypeptides. • The polypeptide chain grows longer as new tRNA molecules are brought in and the “used” tRNA molecules move out. Translation: A Review • The process occurrs until a stop codon is reached. • The final product is a unique polypeptide whose amino acid sequence corresponds to the nucleotide sequence of mRNA, and ultimately, DNA. Question 1 What is the role of the ribisome in protein synthesis? Answer The ribosome binds to mRNA and tRNA and assembles the amino acids in the order needed for the protein to be synthesized. Question 2 What is an anticodon, and what does it represent? Answer An anticodon is a sequence of three nucleotides on the tRNA molecule that binds to a codon of the mRNA strand. Question 3 What happens when a stop codon is reached during translation? Answer When a stop codon is reached, translation ends and the amino acid strand is released from the ribosome. Question 4 What amino acid is coded for by the mRNA codon CAU? Answer His Question 5 What amino acid is coded for by the DNA sequence CAT? Answer Val Question 6 What anticodon would bond to the mRNA codon GAC? A. CTG B. CUG C. GAC D. GUC The answer is B. Translation: RNA to Protein Objectives • Describe the structure and function of DNA and its role in DNA replication.