Control of Gene Activity Chapter 17

Controlling gene activity Remember to control the cell one must control protein synthesis. Remember to control the cell one must control protein synthesis. Protein synthesis can be controlled several different ways. What are some ways to potentially control protein synthesis: Protein synthesis can be controlled several different ways. What are some ways to potentially control protein synthesis: Blocking production of mRNA, tRNA, or rRNA Blocking production of mRNA, tRNA, or rRNA Blocking ribosome production Blocking ribosome production Blocking intake of Amino Acids Blocking intake of Amino Acids Bind a substance to the finished protein that does not allow the protein to function. Bind a substance to the finished protein that does not allow the protein to function.

4 General methods of controlling gene expression in Eukaryotes 1. Transcriptional control: various mechanisms which control which genes are transcribed. 1. Transcriptional control: various mechanisms which control which genes are transcribed. Also controls the rate of transcription. Also controls the rate of transcription. All transcriptional control mechanisms occur in the nucleus. All transcriptional control mechanisms occur in the nucleus. Chromatin plays a role in transcriptional control. Chromatin plays a role in transcriptional control.

2. Posttranscriptional control Occurs in the nucleus after DNA has been transcribed into primary mRNA. Occurs in the nucleus after DNA has been transcribed into primary mRNA. Causes differences in the processing of mRNA Causes differences in the processing of mRNA Affects the maturation rate of mRNA Affects the maturation rate of mRNA Affects the rate which mature mRNA leaves the nucleus Affects the rate which mature mRNA leaves the nucleus

3. Translational control Occurs in the cytoplasm after mRNA leaves the nucleus. Occurs in the cytoplasm after mRNA leaves the nucleus. Affects the “lifespan” of the mRNA Affects the “lifespan” of the mRNA May affect the ability of mRNA to bind to the ribosome. May affect the ability of mRNA to bind to the ribosome.

4. Posttranslational control Occurs in the cytoplasm. Occurs in the cytoplasm. Occurs after the protein is synthesized Occurs after the protein is synthesized Compounds may prevent the protein from undergoing conformational changes necessary for its function. Compounds may prevent the protein from undergoing conformational changes necessary for its function. Compounds bind to the completed protein and limit its ability to function. Compounds bind to the completed protein and limit its ability to function.

Cancer Cancer cells seem to have lost the ability to control gene expression. Cancer cells seem to have lost the ability to control gene expression. Cancer cells lack differentiation. They are not specialized. Cancer cells lack differentiation. They are not specialized. Cancer cells live longer than normal cells. A normal cell enters the cell cycle about 50 times and then dies. Cancer cells live longer than normal cells. A normal cell enters the cell cycle about 50 times and then dies. In cell culture experiments, a cancer cell entered the cell cycle repeatedly. It only died when it ran out of nutrients. In cell culture experiments, a cancer cell entered the cell cycle repeatedly. It only died when it ran out of nutrients.

Cancer cells (continued) Cancer cells have abnormal nuclei Cancer cells have abnormal nuclei Cancer cells form tumors. Cancer cells form tumors. Cancer cells lack normal contact inhibition. Cancer cells lack normal contact inhibition. Contact inhibition-when a cell comes in contact with its neighbor, it stops dividing. Contact inhibition-when a cell comes in contact with its neighbor, it stops dividing. Causes normal cells to form layers. Causes normal cells to form layers. Cancer cells continue to replicate and pile up on each other in large masses - tumors Cancer cells continue to replicate and pile up on each other in large masses - tumors

tumors Angiogenesis- ability of cancer cells to spur blood vessel formation. Angiogenesis- ability of cancer cells to spur blood vessel formation. Some forms of cancer treatment are investigating methods to suppress blood vessel growth to tumors and “starving” the cancer to death. Some forms of cancer treatment are investigating methods to suppress blood vessel growth to tumors and “starving” the cancer to death. Metastasis- Ability of tumors to establish new tumors distant from the primary tumor. (malignancy) Metastasis- Ability of tumors to establish new tumors distant from the primary tumor. (malignancy)

Vocab (refresher from labs) Cancer- a malignant tumor whose nondifferentiated cells exhibit loss of contact inhibition, uncontrolled growth, and the ability to invade tissue and metastasize. Cancer- a malignant tumor whose nondifferentiated cells exhibit loss of contact inhibition, uncontrolled growth, and the ability to invade tissue and metastasize. Oncogene- A cancer causing gene through mutation. Oncogene- A cancer causing gene through mutation. Operon- A group of structural and regulating genes that function as a single unit. Operon- A group of structural and regulating genes that function as a single unit. Operator- sequence of DNA that a repressor protein binds to. Operator- sequence of DNA that a repressor protein binds to. Inducer- A molecule that brings about activity of an operon by joining with a repressor and preventing it from binding to the operator. Inducer- A molecule that brings about activity of an operon by joining with a repressor and preventing it from binding to the operator.

Vocab (continued) Regulator gene- in an operon, a gene that codes for a repressor Regulator gene- in an operon, a gene that codes for a repressor Repressor- A protein molecule that binds to the operator, prevents polymerase from binding to the promoter site of an operon. Repressor- A protein molecule that binds to the operator, prevents polymerase from binding to the promoter site of an operon. Promoter- location on an operon where transcription begins. Promoter- location on an operon where transcription begins. Carcinogen- an environmental agent that causes mutations leading to the development of cancer. Carcinogen- an environmental agent that causes mutations leading to the development of cancer.

Cancer treatments Preventative surgery – removal of tissues at risk of becoming cancerous (mastectomy) Preventative surgery – removal of tissues at risk of becoming cancerous (mastectomy) Chemotherapy – treatment of disease with the use of chemicals. Adversely affects cancerous cells as well as healthy tissue. Chemotherapy – treatment of disease with the use of chemicals. Adversely affects cancerous cells as well as healthy tissue. Radiation therapy – treatment of a disease using radiation. Targets specific cancer cells, but also affects healthy tissue as well. Radiation therapy – treatment of a disease using radiation. Targets specific cancer cells, but also affects healthy tissue as well. Mastectomy & oophorectomy - Removal of affected tissue Mastectomy & oophorectomy - Removal of affected tissue Proton therapy – Firing protons into affected tissue. The positive charge delivers more energy to the targeted cells and has shown promise as a cancer treatment. Proton therapy – Firing protons into affected tissue. The positive charge delivers more energy to the targeted cells and has shown promise as a cancer treatment.

Cancer Prevention Don’t Smoke Don’t Smoke Don’t sunbathe Don’t sunbathe Avoid Alcohol Avoid Alcohol Avoid Radiation Avoid Radiation Get tested for cancer Get tested for cancer chemoprevention chemoprevention Be aware of occupational hazards Be aware of occupational hazards Be aware of hormone therapy Be aware of hormone therapy Eat a healthy diet Eat a healthy diet Genetic testing for predisposition to cancer. Genetic testing for predisposition to cancer.