NOTES: 10.3-10.4 Regulating the Cell Cycle / Cell Differentiation

10.3: Regulating the Cell Cycle Key Concepts: How is the cell cycle regulated? How are cancer cells different from other cells? What causes cancer?

The Cell Cycle – review of the basics: Genetic information is in the form of DNA Cell cycle = process of cell division  The cell grows;  DNA is copied;  The contents of the nucleus are divided;  Cytoplasm is divided;  Two new cells exactly like the original cell!

Also, recall… one of the major characteristics of living things is the ability to GROW an adult doesn't have bigger cells, they have more cells You can grow too many cells!!!

An Interesting Fact About Cell Division: Not all cells move through the cell cycle at the same rate Ex: most muscle cells & nerve cells do not divide at all once they have developed Ex: skin cells and cells lining our intestines complete the cell cycle every 24-28 hours Ex: frog embryo cells take less than one hour!

Controls on Cell Division Controls can be observed in a lab Cells in a petri dish containing nutrient broth (food) will grow and divide forming a thin layer When the cells come into contact with each other, they stop growing

Controls on Cell Division continued… If cells from the center are removed, growth and division will continue until cells are in contact with each other once again When have you witnessed this happening with your own body?

Cell Cycle Regulators Several scientists discovered that cells undergoing cell division (mitosis) contained a protein/enzyme If this protein was injected into a nondividing cell, the mitotic spindle would start to form Scientists called this protein CYCLIN Scientists have since discovered a family of closely related proteins (cyclins) & dozens of other proteins that help regulate the cell cycle

Regulatory Proteins: The cell cycle is controlled by regulatory proteins, both inside & outside of the cell

Regulatory Proteins: INTERNAL Respond to events occurring inside a cell Allow the cell cycle to proceed only when certain events have occurred in the cell itself Example: some regulatory proteins make sure a cell does not enter mitosis until its chromosomes have been replicated Example: a regulatory protein prevents a cell from entering anaphase until the spindle fibers have attached to all chromosomes.

Regulatory Proteins: EXTERNAL Respond to events occurring outside the cell GROWTH FACTORS: stimulate growth & division of cells -important during embryo development & wound healing Other external regulators cause cells to slow down or stop their cell cycles…this prevents excessive cell growth & keeps body tissues from disrupting one another.

Recent studies suggest… The portion of interphase just before DNA replication is a key control period in the cell cycle; There are several regulatory proteins identified as controlling the cell cycle… RECALL: proteins are coded for by DNA! So…

A mistake (MUTATION) in the DNA (GENES) that codes for one or more of these control factors/enzymes could lead to a LOSS OF CONTROL OF THE CELL CYCLE.

Uncontrolled Cell GroWth What can happen if the cell cycleis not regulated so carefully? CANCER!! Cancer cells do not respond to signals that regulate the growth of most cells. cancer cells

The result? They form masses of cells called TUMORS that can damage the surrounding tissues Benign vs. malignant Cancer cells can also break off and spread throughout the body METASTASIS BREAST TUMOR Old Mastectomy Vs. New Mastectomy

Recent Research Cancer is a disease of the cell cycle Many cancer cells have a defect in a gene called p53 The protein made from this gene normally halts the cell cycle until all chromosomes have been replicated properly (without mutations) If it isn’t working, damaged DNA can replicate The cell may have lost the information it needs to respond to growth control signals Cancer is a disease of the cell cycle

Cancer is the 2nd leading cause of death in the U.S. It can affect any tissue, but the most commonly affected are:  lung  colon  breast  prostate

What causes the loss of growth control? Smoking tobacco Radiation exposure Viral infection HUMAN LUNG

Cancer Prevention: ● There is a clear link between healthy lifestyle and reducing the incidence of cancer; ● Diet low in fat and high in fiber; (fruits, vegetables, & grains) ● Vitamins and minerals; (A, C, E, & calcium) ● Exercise; ● Wear sunscreen

● DON’T SMOKE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! (Seriously!! This should be a no-brainer!!)

Treatments surgery (for benign tumors) radiation chemotherapy

10.4: Cell Differentiation Key Concepts: How do cells become specialized for different functions? What are stem cells? What are some possible benefits & issues associated with stem cell research?

Cell Differentiation: ● the process by which cells become specialized for different functions; ● we all started as an individual fertilized egg cell  embryo  adult organism ● cell differentiation is controlled by a number of interacting factors in an embryo…many of which we still don’t completely understand!

STEM CELLS: ● how do so many specialized, differentiated cell types develop from just a single cell? ● such a cell is said to be TOTIPOTENT ● TOTIPOTENT = able to develop into any cell type in the body ● PLURIPOTENT = able to develop into most of the body’s cell types

STEM CELLS: ● STEM CELLS = the unspecialized cells from which differentiated cells develop ● TYPES of stem cells: ● EMBRYONIC: pluripotent cells found in early embryo stages…mouse embryonic stem cells have been triggered to differentiate into: nerve cells, muscle cells, & even sperm & egg cells!

STEM CELLS: ● TYPES of stem cells: ● ADULT: groups of cells that differentiate to renew & replace cells in the adult body; more limited than embryonic stem cells ● Example: adult stem cells in the bone marrow can develop into several types of blood cells ● Example: adult stem cells in the brain can produce neurons or nerve cells

STEM CELLS: ● BENEFITS of Stem Cell Research: ● stem cells offer excellent prospects to repair cellular damage that is the cause of many human life-threatening conditions: ● Example: heart attacks destroy heart cells ● Example: strokes & spinal cord injuries destroy nerve cells & cause paralysis

STEM CELLS: ● ETHICAL ISSUES: ● adult stem cells can be harvested from willing adult donors ● embryonic stem cells are harvested from early stage embryos…this has led to many ethical discussions involving issues of life and death… ● in the future, technology may help to reduce these ethical concerns (i.e. reprogram an adult stem cell to behave like an embryonic stem cell)