Chapter 11Gene Expression

I. Role of Gene Expression Gene expression is the activation

(“turning on”) of a gene ◦Separation of fingers and toes

Genome: complete genetic material contained in an individual

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Discovered in the early 1960’s by Francois Jacob and Jacques Monod

they were studying how genes control the metabolism of sugar lactose (found in milk) in E. coli

Prokaryotes

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Regulator genes code for repressor proteins which stop a gene from being expressed

Absence of Lactose

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Lactose binds to the repressor protein forcing it to detach and allowing RNA polymerase to begin transcription producing mRNA

Presence of Lactose

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Much more complex than prokaryotes Multicellular Contain genetic information within the

nucleus

Eukaryotes

http://deltabiology.com/wp-content/uploads/2011/07/cell-anatomy.jpg

Euchromatin- site of active transcription in DNA and RNA

**Some portions remain permanently coiled in chromosomes-these genes can never be transcribed**

Introns- transcribed but NOT translated Exons- BOTH transcribed and

translated

Structure of Eukaryotic Genes

Pre-mRNA◦ Contains both introns and exons◦ Exon splicing occurs turning pre-mRNA into mRNA

Control after Transcription

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Path from DNA to Proteins

library.thinkquest.org/C006188/basics/rna.htm

Cell Differentiation – cells have specific jobs within the cell◦Muscle cells-specialize in movement◦Red blood cells-carry oxygen◦Liver Cells-break down fat

Morphogenesis- development of structure in an organism

II. Gene Expression in Development

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Determine where anatomical structures develop during morphogenesis

◦Anntennapedia-mutation occurring in this gene that makes a leg grow where an antenna should be

Homeotic Genes

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Cells are constantly switching genes on and off

DNA chip- used for tracking gene expression◦Fragments are tagged with a fluorescent

compound which lights up when that gene is turned on

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III.Cancer Cancer- uncontrolled growth of cells that invades other parts of the body

Proto-oncogenes- regulate cell growth and division◦Mutations change a proto-oncogene into an oncogene

Oncogene- uncontrolled cell division and over expression of proteins at the wrong time

Tumor- abnormal proliferation of cells◦Benign- growth that doesn’t spread◦Malignant-invades and destroys tissues at different places within the body- metastasis

Tumors

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Carcinogen-any substance that promotes cancer (ex. Tobacco smoke, UV rays, viruses)◦Mutagens- agents that cause mutations to occur

with in a cell

Causes of cancer

Kinds of CancerCarcinomas- grow in the tissues lining organs

Sarcomas-grow in bone and muscle tissue

Lymphomas-solid tumors growing in the lymphatic system

Leukemia- uncontrolled growth in blood tissues.Viruses – stimulate uncontrolled growth in host cells causes some

cancers in blood forming tissues and HPV which causes cervical cancerThese 3 cancers can occur anywhere within the body but they get there

name from the place they start

Whether you are 2 or 92, cancer affects us all. Whether you are black or white, red, brown or, yellow, Cancer does not discriminate! Everyone is susceptible to cancer... you... your spouse... cancer doesn't care if you are rich, poor or somewhere in between.