BIOL 3451 1st Edition Lecture 18 Outline of Last Lecture I. 13.11 Transcription in Eukaryotes Differs from Prokaryotic Transcription in Several WaysII. 13.12 The Coding Regions of Eukaryotic Genes Are Interrupted by Intervening SequencesIII. 13.13 RNA Editing May Modify the Final TranscriptIV. 13.14 Transcription Has Been Visualized by Electron MicroscopyV. 14.1 Translation of mRNA Depends on Ribosomes and Transfer RNAsVI. 14.2 Translation of mRNA Can Be Divided into Three StepsOutline of Current Lecture I. 14.3 High-Resolution Studies Have Revealed Many Details about the Functional Prokaryotic RibosomeII. 14.4 Translation Is More Complex in EukaryotesIII. 14.5 The Initial Insight That Proteins Are Important in Heredity Was Provided by the Study of Inborn Errors of MetabolismIV. 14.6 Studies of Neurospora Led to the One-Gene: One-Enzyme HypothesisV. 14.7 Studies of Human Hemoglobin Established That One Gene Encodes One PolypeptideVI. 14.8 The Nucleotide Sequence of a Gene and the Amino Acid Sequence of the Corresponding Protein Exhibit ColinearityVII. 14.9 Variation in Protein Structure Provides the Basis of Biological DiversityVIII. 14.10 Posttranslational Modification Alters the Final Protein ProductIX. 14.11 Proteins Function in Many Diverse RolesX. 14.12 Proteins Are Made Up of One or More Functional DomainsXI. 15.1 Gene Mutations Are Classified in Various WaysXII. 15.2 Spontaneous Mutation Arise from Replication Errors and Base ModificationsCurrent LectureI. 14.3 High-Resolution Studies Have Revealed Many Details about the Functional Prokaryotic Ribosomeo Crystal structures of individual ribosomal subunits and the intact 70S bacterial ribosome have been solved- Viewed entire translational complex at atomic level- These studies provide many details about ribosomal function and the importance of the rRNA comoponentII. 14.4 Translation Is More Complex in EukaryotesThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o Eukaryotes:- Ribosomes are larger and longer lived than in bacteria - Transcription in nucleus 5’ end of mRNA capped, remove introns, and put a poly-A tail on 3’ end of mRNA- Translation in cytoplasm- Many (50%) mRNAs contain a purine three bases upstream of AUG and called: Kozak sequence: increases the efficiency of translation by interacting with the initiator tRNA- Translation generally requires more factors for initiation, elongation, and termination than in bacteria- Free-floating ribosomes and those with endoplasmic reticulumIII. 14.5 The Initial Insight That Proteins Are Important in Heredity Was Provided by the Study of Inborn Errors of Metabolismo Alkaptonuria and phenylketonuria (can’t metabolize phenylaloline-in soda)- Result from mutations that lead to metabolic blocks- Many medical conditions are caused by errors in metabolism- Pedigree analysis became useful here which showed that human diseases can have genetic basiso Phenylketonuria (PKU): results when phenylalanine is not converted to tyrosine- Phenylalanine hydroxylase is inactive in affected individuals- Phenylalanine and its derivatives enter the cerebrospinal fluid with elevated levels, resulting in mental retardation- Newborns are routinely screened throughout US< with afflicted babies put on special dietsIV. 14.6 Studies of Neurospora Led to the One-Gene:One-Enzyme Hypothesiso Beadle and Tatum - Nutritional mutations in bread mold caused loss of enzymatic activity that catalyzes an essential reaction in wild-type organisms- Came up with theory: One gene-one enzyme  Always find one thing V. 14.7 Studies of Human Hemoglobin Established That One Gene Encodes One Polypeptideo Able to show that is was a specific sequence in hemoglobin (sickle-cell anemia)o Many proteins that encode functions have more than one polypeptide; not all proteins are enzymes, and some have more than one subunito 3D conformation is essential to a protein’s specific function- Modified to one gene: one protein then to One gene: one polypeptideo Sickle-cell anemia: recessive genetic disease in which afflicted individuals are homozygous for the HbS hemoglobin allele; heterozygotes are carriers of affected gene, but largely are unaffected- Fingerprinting demonstrated that the HbS and HbA hemoglobins differ by a single peptide fragment (Fig. 14.14)- Hemoglobin genes are developmentally regulated, and different hemoglobins are expressed at different times in human development Getting oxygen from Placenta vs from airVI. 14.8 The Nucleotide Sequence of a Gene and the Amino Acid Sequence of the Corresponding Protein Exhibit Colinearityo Colinearity: order of the nucleotides in a gene correlates directly with the order of amino acids in the corresponding polypeptide- This is trueVII. 14.9 Variation in the Protein Structure Provides the Basis of Biological Diversityo Amino acids attach to tRNA, and are released from ribosomes as polypeptides- Then after translation, they form different structure to interact with other polypeptideso Amino acids have:- Carboxyl group- Amino group- R (radical) group that makes them all different- Fig 14.16o Amino acids connected by peptide bond: formed by - Dehydration reaction between carboxyl group of one amino acid and amino group of another (Fig. 14.17)o Four levels of protein structure:- Primary- Secondary: folding held together hydrogen bonding between atoms on backbone- Tertiary: folding including beta sheet and alpha helix; held together by R groups of polypeptides (hydrogen bonding, covalent bonding)- Quaternary: held together by R groups on different polypeptide chains- 3D conformation of any protein is a product of its primary structureVIII. 14.10 Posttranslational Modification Alters the Final Protein Producto Posttranslational modification: modification of some proteins after they have beensynthesized- Crucial to the functional capability of the final protein product- Some ex. Of translational modification: N-terminus amino acid usually removed or modified Carbohydrates side chains are sometimes attached Polypeptide chains may be trimmed Individual amino acid residues are sometimes modified  Polypeptide chains are often complexed with metal (ions)IX. 14.11 Proteins Function in Many Diverse Roles- Proteins have many different functions in body Hemoglobin and myoglobin transport