Gene Expression via Modern Biology

1. Gene Expressionvia Modern Biology The activation of a gene that results in the formation of a protein

2. Gene expression • Proteins have different functions • Some proteins form a structural role • Others proteins are enzymes that act as catalysts to speed up chemical reactions • Proteins are produced when needed

3. Genome • The complete genetic material in an individual • Gene expression occurs through transcription and translation • Gene expression begins when the enzyme RNA polymerase transcribes the DNA nucleotide sequence of a gene into a specific mRNA • During translation, this mRNA migrates to a ribosome to be translated into a specific protein.

4. Gene Expression in Prokaryotes(simple, single celled organisms) • Structural genes are genes that code for particular polypeptides • Promoter recognizes the enzyme RNA polymerase and promotes transcription • Operator is a DNA segment that is a binding site for an inhibitory protein that blocks transcription and prevents the synthesis of protein. • Promoter + Operator = Operon: series of genes that code for specific products and the elements that regulate or control these genes. Ex: lac operon are structural genes coded for the enzymes that regulate lactose metabolism.

5. Prokaryote Gene Expression con’t. • Repressor protein: inhibits a specific gene from being expressed, the blocking of transcription by the action of this protein is repression • Transcription is controlled by a regulator gene • Inducer: initiates gene expression • Activation is the initiation of transcription by the removal of a repressor protein

6. Gene expression in Eukaryotes ( multicellular organisms) • Genomes are much larger than Prokaryotes • DNA is located in several individual chromosomes • Cells are specialized and differentiated

7. Eukaryotic Gene Structure • Euchromatin: the uncoiled part of a chromosome where active transcription of DNA and RNA take place • Introns: The sections of a structural gene that do not code for amino acids • Exons: The sections of a structural gene that are translated into proteins when expressed

8. Control after Transcription • Introns and exons are transcribed to form Pre-mRNA. Enzymes cut out the introns and join remaining exons together forming mRNA. This leaves the nucleus and travels through the nuclear pore to the cytoplasm where translation occurs.

9. Enhancer control • Enhancer are noncoding control sequences that produce transcription, this must be activated for its associated gene to be expressed. • Transcription factors bind to enhancers and RNA polymerase to regulate transcription • Many enhancers are located far away from their genes they need to activate. • Transcription factors bend the DNA strand to bring the enhancer close to the RNA polymerase so transcription can begin.

10. Cell Differentiation • The development of cells having specialized function • Morphogenesis is the growth and development of these organs and tissue into an organism • Homeotic genes are regulatory genes that determine where certain anatomical structures like appendages will develop in an organism • Homeobox is the specific DNA sequence that regulates patterns of development.

11. Cancer • A tumor is uncontrolled, abnormal cell division • Benign tumors remain within a mass and are usually not life threatening • Malignant tumors are uncontrolled dividing cells that invade and destroy healthy tissues all over the body. • Metastasis is the spread of the cancer beyond their original site

12. Kinds of Cancer • Carcinomas grow in the skin and tissues that line the organs • Sarcoma grow in bone and muscle tissue • Lymphomas are solid tumors that grow in the tissue that form blood cells • Leukemia are tumors in blood forming tissues that produce an uncontrolled amount of white blood cells

13. Causes of Cancer • Normal cells will stop dividing when crowded, cancer cells keep dividing ignoring the cellular message • Growth factors are not controlled in a proper sequence at a proper rate which are mutations in gene expression. • Carcinogens increase the risk of cancer • Mutagens are carcinogens that cause mutations to occur. • Usually more than one mutation is needed to produce cancer

14. Oncogenes • They are a gene that causes cancer or other uncontrolled cell growth • Proto-oncogenes are normal genes that control a cells growth and differentiation • Tumor-suppressor genes code for proteins that prevent uncontrolled rate of cell division. • Viruses can cause cancer and stimulate uncontrolled cell growth and mutations.