MCB 181 1st Edition Lecture 25Outline of Previous Lecture I. Mendel’s Concepts (Continued)II. Extending Mendel’s RulesOutline of Current Lecture I. The Genetic CodeII. Genetic Code MutationsIII. Clicker QuestionsCurrent LectureI. The Genetic Codea. The one-gene, one enzyme hypothesis proposed that genes contain the information needed to make proteins, many of which function as enzymesb. The central dogma summarizes the flow of information in cellsc. Genetic information flows from DNA RNA Proteinsd. Differences in genotype may cause differences in phenotypes e. A codon is a group of three bases that specify a particular amino acidf. Analyzing the Codei. The code is redundant – all amino acids except methionine and tryptophan are coded by more than one codonii. The code is unambiguous – a single codon never codes for more than one amino acidiii. The code is non-overlapping – once the ribosome locks onto the first codon, it then reads each separate codon one after anotheriv. The code is nearly universal – with a few minor exceptions, all codons specifythe same amino acids in all organismsv. The code is conservative – when several codons specify the same amino acid,the first two bases in those codons are almost always identicalII. Genetic Code Mutationsa. A mutation is any permanent change in an organism’s DNAb. DNA mutations change the genotype of a cell. This leads to the production of novel types of proteins and can effect phenotypes c. Point mutations – single base change mutationi. Point mutations can result from errors in DNA replicationii. Unrepaired mistakes in DNA synthesis lead to point mutationsIII. Clicker QuestionsAssertion ReasonA mutation in the gene that encodes the RNA primase willprevent the DNA Polymerase from replicating the DNA moleculeBecauseDNA Polymerase II requires anavailable free 3’ hydroxyl molecule to start the polymerization of DNAAssertion is true; Reason is true; Reason is the correct
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