BIO111_Lecture_3-Gene_Expressions.

BIO111_Lecture_3-Gene_Expressions. - BIO111 Lecture 3-Gene...

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BIO111 Lecture 3-Gene Expressions Enzymes and Genetics -George Beadle & Edward Tatum, 1941. -Studied the fungus Neurospora crassa. -Used X-rays to damage the DNA in cells, to create mutants quickly. -Isolate cells w/mutant alleles of Arg genes. -Arg genes: used in biochemical synthesis of the amino acid arginine. -Mutants identified by failure to make Arginine. -Media contains Arg=growth. -Media contains no Arg=no growth. Biochemical Pathways -Correlate with biochemical pathway. -Biochemical pathways involve multiple steps. -Multiple enzymes used in a specific order. -Indentify each Arg mutant with media containing intermediates. FIGURE 15.1 Giving the medium different intermediates used to make Arginine. Only some Arg growth depending on the mutation in the enzyme and which intermediate has been giving. The damaged DNA correlates to the damage enzyme. Genes encode enzymes -Beadle & Tatum proposed that each enzyme of the arginine pathway was encoded by a separate gene. -They proposed the one gene-one enzyme hypothesis. -Today we know this as the one gene-one polypeptide hypothesis. -Multiple polypeptides make up a protein. The Central Dogma -The central dogma of molecular biology states that information flows in one direction: DNA RNA protein -Transcription is the flow of information from DNA to RNA. -Translation is the flow of information from RNA to protein. How information flows in a cell. FIGURE 15.2 DNA molecule used as a template. Transcribe, translate. Gene Expression -The Central Dogma describes gene expression.
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Gene expression: accessing and using the information encoded on a particular stretch of DNA (often to build a protein) -The when and where of gene expression is tightly controlled. -Conversion of genotype phenotype. -Still oversimplification but good starting point. -Use DNA as a template and synthesizing a strand of RNA, to help build a protein. Overview -DNA stores information and is copied. -RNA: temporary copy of DNA information. -RNA polymerase: RNA synthesis enzyme. -RNA is used to direct synthesis of proteins. -Some more recent advancements: -ncRNA: non-coding RNA, regulate expression, ribosome structure. Control the when & the where of gene expression…. Reverse transcription: DNA made from RNA (Retroviruses store DNA permanently, take info from RNA, put into DNA and transfer info that way). Genetic Code -Need to understand informatics. -Relate information in DNA to information in protein. -The order of a string of nucleotides is the information necessary to make a protein. -Give the DNA meaning. Get them in right order, reading them in the right framework. -Nucleotides are read in groups of 3 CODONS. How many bases needed? -DNA “alphabet” to protein “alphabet”. -DNA alphabet=nucleotides. Protein alphabet=amino acids.
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