Prokaryote Gene Regulation

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Presentation transcript:

Prokaryote Gene Regulation Chapter 12 Molecular Genetics 12.4 Gene Regulation and Mutation Prokaryote Gene Regulation Ability of an organism to control which genes are transcribed in response to the environment An operon is a section of DNA that contains the genes for the proteins needed for a specific metabolic pathway. Operator: on/off switch Promoter: where RNA polymerase binds to DNA Regulatory gene Genes coding for proteins

The Trp Operon 12.4 Gene Regulation and Mutation Chapter 12 Molecular Genetics 12.4 Gene Regulation and Mutation The Trp Operon

The Trp Operon (in the bacteria E. coli) Chapter 12 Molecular Genetics The Trp Operon (in the bacteria E. coli) The tryptophan (trp) operon is the cluster of DNA that controls whether or not this amino acid is transcribed. Repressible operon: can be turned off by a repressor protein

The Trp Operon (in the bacteria E. coli) Chapter 12 Molecular Genetics The Trp Operon (in the bacteria E. coli) HIGH trp Levels – Trp operon “off” Trp binds to the repressor protein which becomes activated. Activated repressor proteins inhibit RNA polymerase from binding and transcribing DNA.

The Trp Operon (in the bacteria E. coli) Chapter 12 Molecular Genetics The Trp Operon (in the bacteria E. coli) LOW trp Levels – Trp operon “on” Trp doesn’t bind to the repressor protein which is inactivated. Inactivated repressor proteins do not block RNA polymerase from binding and transcribing DNA.

The Lac Operon (opposite of trp operon) Chapter 12 Molecular Genetics 12.4 Gene Regulation and Mutation The Lac Operon (opposite of trp operon) An inducible operon that transcribes for enzymes When lactose is present, the lac operon enables the creation of these enzymes to use lactose as energy.

The Lac Operon “Off” No lactose is present Chapter 12 Molecular Genetics 12.4 Gene Regulation and Mutation The Lac Operon “Off” No lactose is present The repressor protein in active and prevents transcription When no lactose is present, the RNA polymerase cannot bind to the lac operon.

The Lac Operon “On” Lactose is present Chapter 12 Molecular Genetics 12.4 Gene Regulation and Mutation The Lac Operon “On” Lactose is present Allolactose is an inducer that binds to the repressor protein to inactivate the protein. The repressor protein is inactive and enables transcription. Inducible operon: turned on by inducer.

Eukaryote Gene Regulation Chapter 12 Molecular Genetics 12.4 Gene Regulation and Mutation Eukaryote Gene Regulation Controlling transcription Transcription factors ensure that a gene is used at the right time and that proteins are made in the right amounts Forms complexes to guide and stabilize binding of RNA polymerase to promoter Regulatory proteins control the rate of transcription.

Eukaryote Gene Regulation Chapter 12 Molecular Genetics 12.4 Gene Regulation and Mutation Eukaryote Gene Regulation Controlling transcription The complex structure of eukaryotic DNA (DNA wrapped around histones to form nucleosomes) also regulates transcription.

During development, cells become specialized. Chapter 12 Molecular Genetics 12.4 Gene Regulation and Mutation Hox Genes During development, cells become specialized. Hox (homeobox) genes are responsible for the general body pattern of most animals.

RNA Interference (RNAi) Chapter 12 Molecular Genetics 12.4 Gene Regulation and Mutation RNA Interference (RNAi) RNA interference can stop the mRNA from translating its message. Small pieces of double-stranded RNA are cut by a dicer This interfering RNA binds to a protein complex then binds to a region of mRNA to be cut

A permanent change that occurs in a cell’s DNA is called a mutation. Chapter 12 Molecular Genetics 12.4 Gene Regulation and Mutation Mutations A permanent change that occurs in a cell’s DNA is called a mutation. Types of mutations Point mutation Insertion Deletion

12.4 Gene Regulation and Mutation Chapter 12 Molecular Genetics 12.4 Gene Regulation and Mutation

Chapter 12 Molecular Genetics 12.3 Gene Regulation and Mutation Copy and paste the link below into a web browser for practice with identifying mutations: (Click on the link under Interactive Tables called Mutations – A and Mutations – B) http://glencoe.mcgraw-hill.com/sites/0078802849/student_view0/unit3/chapter12/concepts_in_motion.html#

Protein Folding and Stability Chapter 12 Molecular Genetics 12.4 Gene Regulation and Mutation Protein Folding and Stability Substitutions also can lead to genetic disorders. Can change both the folding and stability of the protein

Can occur spontaneously Chapter 12 Molecular Genetics 12.4 Gene Regulation and Mutation Causes of Mutation Can occur spontaneously Chemicals and radiation also can damage DNA. High-energy forms of radiation, such as X rays and gamma rays, are highly mutagenic.

Body-cell v. Sex-cell Mutation Chapter 12 Molecular Genetics 12.4 Gene Regulation and Mutation Body-cell v. Sex-cell Mutation Somatic cell mutations are not passed on to the next generation. Mutations that occur in sex cells are passed on to the organism’s offspring and will be present in every cell of the offspring.