The Clicker: human dystophin gene contains 2.4 million base pairs with 79 exons, while the final (mature) mRNA transcribed from this gene is 14,000 base pairs. What percentage of the DNA is this gene actually codes for the protein? .5%
Genetic Code mRNA nucleotides Triplet Cide Degenerate or redundant code rRNA and tRNA involbved in this process rRNA as part of the ribosome (site of protein synthesis) tRNA anti-codon and an amino acid TRANSLA TION: initiation: 5' end of mRNA binds to the small ribosomal subunit and the first codon (AUG) (always the first codon) pairs with a tRNA with the anticodon to AUG this tRNA carries the amino acid methionine. The large subunit now binds to form a functional ribosome (P site) Figure 17.17 chain elongation: the ribosome can bind 2 tRNAs (each with 1 amino acid). One in the P (peptidyl) site and the other in the A (aminoacyl) site. Peptide bonds between form the amino acids attached to the tRNAs and the tRNA in the P site is released. ribosome moves 3 nucleotides at a time About making the polypeptide chain; taking amino acids and joining them together; have a second tRNA through the A site, have the anti-codon and another amino acid; (Figure 17.18) A site, P site, E site; Moves 3 nucleotides at a time; termination message: when ribosome reaches a stop codon (UAA, UAG, UGA) the newly formed polypeptide is released. (Figure 17.19) Insert releasing factor: 1. break the body between molecule so polypeptide chain is free 2. 3. break the molecule apart PKU is caused by the lack of functional phenylalanine hydroxylase enzyme.
Phenylalanine hydroxylase is 452 amino acids long and several different mutations have been discovered. MUT A TION Point Mutations: Base substitutions: Frame shift mutations: Chromosomal Mutations: