Why do cells divide? Agenda for Friday Dec 19 th 1.Go over test 2.Mitosis notes & video 3.Mitosis...
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Transcript of Why do cells divide? Agenda for Friday Dec 19 th 1.Go over test 2.Mitosis notes & video 3.Mitosis...
Why do cells divide?
Agenda for Friday Dec 19th 1. Go over test2. Mitosis notes & video3. Mitosis worksheet
Grades on wall
Why does a cell divide?• Too large to work efficiently
– Smaller the cell = quicker it can work• Transport of Substances• Cellular communication
– Ratio of surface area to volume
The Cell Cycle
• Cell reaches max size it stops growing or divides– Cells reproduce by growing and dividing = cell cycle
• 3 main stages of cell cycle1. Interphase – cell grows, replicates DNA2. Mitosis – nucleus and nuclear material divide3. Cytokinesis – cytoplasm divides
3 Stages of InterphaseGap 1 (G1)• Right after cell divides, normal functions,
prepares to replicate DNASynthesis (S)• Cell copies DNA (contains genetic material)
– Chromatin is the relaxed form of DNA– Chromosomes are the condensed form of DNA
Gap 2 (G2)• Cell prepares for mitosis
Mitosis• Cell’s DNA separates
– Creates 2 identical daughter cells– Same DNA– Same Number of Chromosomes in each cell
• 4 Stages – Prophase, Metaphase, Anaphase, Telophase
1. Prophase• Chromatin condenses into chromosomes
– X – shaped– Consist of two chromatids – identical copies of DNA– Chromatids are connected at a centromere
1. Prophase
• Nuclear membrane disappears • Spindle apparatus appears
– Spindle fibers, centrioles, and aster fibers– Helps move chromosomes
4. Telophase
• Chromosomes arrive at the poles• Chromosomes unwind (back to chromatin)• Two nuclear membranes begin to form• Spindle apparatus disappears
Cytokinesis
• Divides cytoplasm
• Animal Cells– Microfilaments constrict/pinch the cytoplasm
• Plant Cells– Cell plate forms between two daughter nuclei – Cell walls then form on either side of cell plate
Explain what happens in each step of mitosis.
Agenda for Monday Jan. 5th 1. Review mitosis (video)2. Go over HW3. Mitosis Cell Lab
• https://www.youtube.com/watch?v=L0k-enzoeOM
If a cell has 150 chromosomes how many daughter cells are created at the
end of mitosis? How many chromosomes are in each cell?
Agenda for Tuesday Jan 6th 1. Finish mitosis onion cell lab
http://www.sumanasinc.com/webcontent/animations/content/mitosis.html
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__mitosis_and_cytokinesis.html
Cancer Vocab• Cancer – uncontrolled growth and spread of
abnormal cells• Neoplasm – new growth of tissue that serves
no physiological function• Tumor – clumping of neoplasmic cells• Malignant - cancerous• Benign - noncancerous• Biopsy –examination of cell development
Skin Cancer• The ABCD’s of melanoma (skin cancer):
– Asymmetry: one half is not like the other– Border: the edges are jagged or irregular– Color: the color is varied, tan, red, black ect– Diameter: the diameter is larger than 8mm
(the top of a pencil eraser
A
B
C
D
Cancer
• Uncontrolled cell division
• Tumors begin with a single cell that reproduces by mitosis– Cells in tumors divide continuously
• Metastasis: Process in which cells are invasive and move to other sites in the body
How does it happen?
• Two classes of genes: Oncogenes and tumor suppressor genes– Proto-oncogenes: control cell division – Tumor suppressor genes turn off cell division
p. 181
4Cell
division
Mitosis
3DNA
repair
G21
Cell grows,
doubles in size
G1
S
2Chromosome
duplication
G2/M checkpoint
G1/S checkpoint
Stepped Art
• Checkpoints in the cell cycle regulate cell division
The Cell Cycle and Cancer
• Neoplasm- abnormal growth of cells • Benign neoplasms are not cancerous
– Encapsulated; Do not invade neighboring tissue or spread
• Malignant neoplasms are cancerous – Not encapsulated; Readily invade neighboring
tissues – May also detach and lodge in distant places –
metastasis
Stages of Cancer
• 4 stages, – 1 = not so bad – 4 = really bad
• Stage I – localized to one part of the body Stage II - locally advanced
• Stage III - also locally advanced• Stage IV - often metastasized, or spread
Causes of Cancer
• Mutation: change in genetic makeup
• A factor which brings about a mutation is called a mutagen.
• Any agent that causes cancer is called a carcinogen and is described as carcinogenic.
Lifestyle Risks
• Smoking
• Diet high fat and low in fruits and vegetables
• Lack of exercise
• Unprotected exposure to the sun, (UV) rays
• Obesity
Environmental Risks
• Second hand smoke
• Air pollution
• Industrial pollution
• Chemical exposures– tar from cigarettes– some foods
Inherited Risks
• Less than 15% of cancers are inherited• Gene mutations are linked to some inherited
cancers• Cancers that may be caused by inherited gene
mutations are:– Colon cancer– Breast cancer– Ovarian– Prostate cancer– Skin cancer
• Some families are more susceptible to getting certain cancers. – Remember you can’t inherit cancer its just that you
maybe more susceptible to getting it.
Stress
• There is connection between stress, immune system and cancer, that is changing the direction of research – it now appears that cancer cells make proteins
that actually tell the immune system to let them alone and even to help them grow.
Other ways• Many forms of cancer related to:
– Physical surroundings– Personal behavior– Or both
• At least 50% of all cancer can be attributed to some type of environmental factor
Treatment
Chemotherapy treatment • uses medicine to weaken and destroy cancer
cells in the body, including cells at the original cancer site and any cancer cells that may have spread to another part of the body.
• a systemic therapy, which means it affects the whole body by going through the bloodstream.
TreatmentRadiation therapy (also called radiotherapy)• high-energy rays are used to damage cancer
cells and stop them from growing and dividing.
• A specialist in radiation therapy is called a radiation oncologist
• Like surgery, radiation therapy is a local treatment; it affects cancer cells only in the treated area
Cancer Prevention
Healthy lifestyle • Exercise and proper breathing • Balanced diet• Complete rest and sleep • Water • Eating Fruit