10/19/ Genes and How They Work Computer Filename: genes2.ppt Hugh B. Fackrell
10/19/ Overview Genes composed of DNA within the chromosome Genes code for proteins DNA is transcribed into RNA RNA is translated into Protein by ribosomes Genes regulated by control of RNA production
10/19/ CODONS sequences of three adjacent nucleotides that code for one amino acid or polypeptide termination 64 codons encrypt of ~ 20 amino acids degenerate RNA: ACU, ACC,ACA, ACG threonine degenerate DNA: TGA, TGG,TGT, TGC threonine
10/19/ Start Codon RNA: AUG DNA: TAC also codes for methionine
10/19/ Stop Codon Nonsense Codons RNA: UAA,UAG,UGA DNA: ATT, ATC, ACT
10/19/ Structure of the Genetic Code DNA : sequences of four nucleotides A,T,G,C CODONS : blueprint for the polypeptide Start & Stop Signals: Where to read the blueprint Regulatory Sequences: When to read the blueprint : operators, enhancers, promotors
10/19/ Interpreting the Genetic Code Two step process : –Transcription DNA --> RNA –Translation RNA--> protein
10/19/ Operon A cluster of functionally related genes and regulator sites transcribed onto single mRNA common in prokaryotes and fungi
10/19/ Transcription occurs in nucleus DNA unravels- single strand RNA Polymerase binds to Promotor site Reads from start sequence(ATG) assembles complementary single strand of RNA (primary RNA) Disengages when reaches stop codon Production of an RNA copy of the gene
10/19/ Transcription Regulation Controlled by DNA Binding proteins that bind to specific nucleotide sequences some bind in the groove of DNA helix some bind to single stranded DNA Promotor site Activator site (positive regulation) Operator site (negative regulation) Enhancer site
10/19/ Promotor Site Controls when DNA transcribed Called TATA box Sequence TTGACA or TATAAT (‘sense’) complementary sequences are AACTGT and ATATTA(‘antisense’) Start codon 30 BP downstream
10/19/ DNA Binding Proteins Negative control :Blocks transcription of DNA to mRNA Postive control: Initiates transcription of DNA to mRNA
10/19/ Negative Control Process is called Repression Process is controlled by a protein called a Repressor Repressor protein has two configurations
10/19/ Operator site sequence of nucleotides between the promotor and the gene binding site for the repressor protein blocks RNA polymerase from reading the gene
10/19/ Tryptophan Repressor: Gene off
10/19/ Tryptophan repressor : gene ON
10/19/ Positive Control process called activation process controlled by a protein called Activator
10/19/ CAP Protein Positive regulator Binds to Outside of DNA Alternative to glucose metabolism Glucose decrease increases CAMP CAMP binds to CAP CAP binds to DNA
10/19/ Gene Regulation (1/6)
10/19/ Gene Regulation (2/6)
10/19/ Gene Regulation (3/6)
10/19/ Gene Regulation (4/6)
10/19/ Gene Regulation (5/6)
10/19/ Gene Regulation (6/6)
10/19/ Question Design a gene regulation system that has an activator that is turned OFF in the presence of a substrate and a promotor that is turned ON in the presence of a product. Define a series of gene regulators that would turn a ‘cascade’ on and then off in series Define, promotor, activator and operator repressor, enhancer