The Ribosome –Is part of the cellular machinery for translation, polypeptide synthesis Figure 17.1
Evidence from the Study of Metabolic Defects In 1909, British physician Archibald Garrod –Was the first to suggest that genes dictate phenotypes through enzymes that catalyze specific chemical reactions in the cell
Nutritional Mutants in Neurospora: Scientific Inquiry Beadle and Tatum causes bread mold to mutate with X-rays –Creating mutants that could not survive on minimal medium; each mutant was defective in a single gene supporting the one gene- one enzyme hypothesis
Overview: the roles of transcription and translation in the flow of genetic information No mRNA processing
Question : RNA (ribonucleic acid) DNA (deoxyribonucleic acid)How does RNA (ribonucleic acid) differ from DNA (deoxyribonucleic acid)?
The triplet code
The dictionary of the genetic code
The stages of transcription: initiation, elongation, and termination
The initiation of transcription at a eukaryotic promoter
RNA processing; addition of the 5 cap and poly(A) tail
The function of the cap is: –prevent mRNA degradation by hydrolytic enzymes –helps attach to the ribosome Function of the 3’ tail: –same functions as the 5’cap –also helps facilitate export of mRNA from nucleus
RNA processing: RNA splicing
The roles of snRNPs and spliceosomes in mRNA splicing
RNA Splicing Removes noncoding regions called introns snRNPs (small nuclear ribonucleoproteins) recognize the splicing signals that are at the ends of introns The RNA in the snRNP is called snRNA (small nuclear RNA) spliceosomes are the larger protein assemblies formed by the joining of snRNPs
Correspondence between exons and protein domains
The structure of transfer RNA (tRNA)
Translation: the basic concept
An aminoacyl-tRNA synthetase joins a specific amino acid to a tRNA
The anatomy of a functioning ribosome
The initiation of translation
The elongation cycle of translation
The termination of translation
Peptide Bonds Join Amino Acids
Polyribosomes
Coupled transcription and translation in bacteria
The signal mechanism for targeting proteins to the ER
The polypeptides of proteins destined for the endomembrane system are marked by a signal peptide, which targets the protein to the ER. A signal recognition particle (SRP) functions as an adaptor that brings the ribosome to a receptor protein built into the ER membrane.
The molecular basis of sickle-cell disease: a point mutation
Categories and consequences of point mutations: Base-pair substitution
Categories and consequences of point mutations: Base-pair insertion or deletion
A summary of transcription and translation in a eukaryotic cell