10/19/2015 1 Genes and How They Work Computer Filename: genes2.ppt Hugh B. Fackrell.

04/20/231

Genes and How They Work

Computer Filename: genes2.pptHugh B. Fackrell

04/20/232

Overview

Genes composed of DNA within the chromosome

Genes code for proteinsDNA is transcribed into RNARNA is translated into Protein by

ribosomesGenes regulated by control of RNA

production

04/20/233

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

04/20/234

Start Codon

RNA: AUG

DNA: TAC also codes for methionine

04/20/235

Stop Codon

Nonsense Codons RNA: UAA,UAG,UGA DNA: ATT, ATC, ACT

04/20/236

Structure of the Genetic Code

DNA : sequences of four nucleotides A,T,G,C

CODONS : blueprint for the polypeptideStart & Stop Signals: Where to read

the blueprintRegulatory Sequences: When to read

the blueprint: operators, enhancers, promotors

04/20/237

Interpreting the Genetic Code

Two step process :

–Transcription DNA --> RNA

–Translation RNA--> protein

04/20/238

Operon

A cluster of functionally related genes and regulator sites

transcribed onto single mRNA common in prokaryotes and fungi

04/20/239

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 geneProduction of an RNA copy of the gene

04/20/2310

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

04/20/2311

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

04/20/2312

DNA Binding Proteins

Negative control :Blocks transcription of DNA to mRNA

Postive control: Initiates transcription of DNA to mRNA

04/20/2313

Negative Control

Process is called Repression Process is controlled by a protein called a

Repressor Repressor protein has two configurations

04/20/2314

Operator site

sequence of nucleotides between the promotor and the gene

binding site for the repressor protein blocks RNA polymerase from reading the

gene

04/20/2315

Tryptophan Repressor: Gene off

04/20/2316

Tryptophan repressor : gene ON

04/20/2317

Positive Control

process called activation process controlled by a protein called

Activator

04/20/2318

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

04/20/2319

Gene Regulation (1/6)

04/20/2320

Gene Regulation (2/6)

04/20/2321

Gene Regulation (3/6)

04/20/2322

Gene Regulation (4/6)

04/20/2323

Gene Regulation (5/6)

04/20/2324

Gene Regulation (6/6)

04/20/2325

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