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CHAPTER 11: Gene Expression

CHAPTER 11: Gene Expression. Recall that gene information codes for the proteins a cell needs for structure & function. **But not all proteins are needed all the time. **How does a cell control when & which proteins are made???. http://upload.wikimedia.org. I. Control of Gene Expression.

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CHAPTER 11: Gene Expression

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  1. CHAPTER 11: Gene Expression Recall that gene information codes for the proteins a cell needs for structure & function. **But not all proteins are needed all the time. **How does a cell control when & which proteins are made??? http://upload.wikimedia.org

  2. I. Control of Gene Expression A. Gene Expression-Is the activation, or “turning on” of a gene that results in transcription & the production of mRNA. • Most of the mRNA is then translated into proteins. • Genome- is the complete genetic material contained in an individual.

  3. B. Prokaryotic Gene Expression • Since prokaryotes are simpler cells (single ring of DNA- no nucleus)- they are easier to study. • Scientists-Francois Jacob & Jacques Monod • in the 1960’s studied E. coli. • discovered how E. coli genes • control the metabolism of sugar (lactose). • Won noble prize 1965. http://zebu.uoregon.edu/~imamura/121/images/e_coli.gif

  4. C. Eukaryotic Gene Expression • Very Different than prokaryotes. • Eukaryotes MUCH more complex. • Operons rarely used. • Multicellular, • Specialized cells • Some cells use different proteins • not all genes expressed at times

  5. 1. Eukaryotic Gene Structure • Chormosomes- tightly coiled DNA for cell division. • Some DNA remains tightly coiled & is not transcribed. • Some DNA uncoils- allows transcription • Euchromatin- uncoiled DNA molecule- • Site of active transcription http://www.llnl.gov/str/June03/gifs/Stubbs1.gif

  6. Turning “on” Different than Prokaryotes • Beyond a promotor are 2 sections of DNA • Introns-DNA section that is transcribed but not translated. • Exons –DNA section that is transcribed AND translated.

  7. Control After Transcription • In eukaryotic nucleus: -Pre-mRNA is made - it’s a large molecule of both introns & exons. -Splicing of introns results in mRNA • mRNA leaves nucleus & goes into cytoplasm where transcription takes place. Section 1 Review Questions p. 222

  8. http://gremlin1.zool.iastate.edu/~volker/img/ps-fig.jpg

  9. II. Gene Expression in Development & Cell Division • All multicellular, sexually reproducing organisms begin life as a zygote (fertilized egg). • Cell Differentiation- the development of cells that have specialized functions. • Morphogenesis- the development of form in an organism.

  10. Homeotic Genes • Regulatory genes that determine where certain anatomical structures, such as appendages, will develop in an organism during morphogenesis. • Considered “master genes” of development. • How they work: • Make regulatory proteins- • switch on certain genes- • controls growth rate in specific areas • Produces structural development.

  11. *Throughout an organism’s life: • Genes are switched on & off • Only a fraction of genes are expressed in any 1 cell. *DNA chip- tool used to track gene expression. -DNA fragments are “tagged” with a florescent compound & when mRNA is studied- look for “light-up” segments. -useful especially in medicine, cancer study.

  12. III. Cancers • Tumor- abnormal proliferation of cells. • Benign Tumor- growth of cells that remains within a mass. (doesn’t spread) • Cancer- uncontrolled growth of cells that can invade other parts of the body.( spreads- more dangerous, deadly)

  13. 2 ways to suppress uncontrolled cell growth. • Tumor suppressor genes – code for proteins that prevent uncontrolled cell division. • Proto-oncogenes- code for proteins that help regulate cell division. • are genes which regulate cell growth. • Ensure events occur properly. A mutation can causes changes in proto-oncogenes or tumor suppressor genes - turns them into Oncogenes. Onogene- gene can cause uncontrolled cell growth.

  14. Metastasis- spread of cancer cells beyond original site. • Carcinogen- any substance that can induce or promote cancer. • Mutagen- agents that cause changes in the cell.

  15. Types of cancers • Carcinoma- growth in the skin, tissues that line the organs of the body. • Sarcomas- grow in bone, muscle tissue. • Lymphomas- solid tumors in lymphatic system tissue. • Leukemia- uncontrolled production of white blood cells.

  16. http://www.cancer-info.com/cancer.gif

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