CONTROL OF CELL DIVISION

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2 CONTROL OF CELL DIVISION Regulation of cell division is necessary to determine when and how cells should divide. Types of Regulators: Internal regulators: Cyclins proteins that regulate the timing of the cell cycle in eukaryotic cells. Other regulator proteins they make sure that certain things happen in the cell before the cell moves to the next phase of the cell cycle (3 major checkpoints in the cell cycle).

3 CONTROL OF CELL DIVISION

4 CONTROL OF CELL DIVISION Regulation of cell division is necessary to determine when and how cells should divide. Types of Regulators: Internal regulators: Cyclins proteins that regulate the timing of the cell cycle in eukaryotic cells. Other regulator proteins they make sure that certain things happen in the cell before the cell moves to the next phase of the cell cycle (3 major checkpoints in the cell cycle). The age of the cell.

5 CONTROL OF CELL DIVISION Regulation of cell division is necessary to determine when and how cells should divide. Types of Regulators: External regulators: Various proteins produced by other cells that speed up or slow down the cell cycle. Cell-to-cell contact if the cell touches other cells, then the cell cycle slows down. Resources if enough space and nutrients are available, growth factors and other proteins make cells divide or speed up their cell cycles.

6 Uncontrolled Cell Division

7 Uncontrolled Cell Division Cancer cells: lack normal checkpoints and continue to grow without inhibition do not respond to normal signals within the cell are not inhibited by other cells. will divide indefinitely. (Cancer cells isolated from a woman in the 1950s continue to grow today.)

8 Tumor Progression 2. Blood vessels feed tumor 4. Secondary tumors form in other parts of the body 1. Tumor growth 3. Tumor cells enter blood and lymph vessels

9 NOVA Cancer Warrier Movie clips on cancer, its nature, and experiments to treat it (Parts 2 and 6) (NOVA Cancer Warrier Entire movie)

10 Types Types of Tumors Benign remains at original site in the body Malignant spreads beyond original site to other parts of body and starts new tumors (metastasis) Types of Cancers Carcinoma originates in external or internal coverings of the body (i.e. skin or lining of intestine) Sarcoma arises in tissues that connect or support other tissues or organs of the body (i.e. bone, cartilage, fat, blood vessels, or muscle) Lymphoma arises in lymph or circulatory systems Leukemia or myeloma involves blood forming tissues and cells (i.e. bone marrow and blood cells) Central Nervous System arise in brain or spinal cord

11 Types of Treatment Prevention Removal of Tumor Surgical removal of tumor is most effective when tumor is in a well-defined area Chemotherapy Chemicals disrupt cell division and stop growth of the tumor Radiation Therapy High energy gamma radiation is aimed at the growing tumor. The radiation damages DNA in the rapidly dividing cells and helps to destroy the tumor. Avoid known carcinogens (cancer-causing agents), such as: UV radiation Tobacco use Perform regular examinations for early detection

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13 X and Y Sex Chromosomes Females have XX Males have XY Humans have 23 pairs of Chromosomes Male determines sex of offspring 22 pairs of autosomes Autosomes Males & females have same autosomes

14 Mutations in DNA Random mistakes during DNA replication Meiosis in Sexual Reproduction Produces millions of unique gametes Random Fertilization Each partner has millions of gametes Which gametes unite is random

15 4 different chromosome line-ups possible: Law of Segregation Pairs of homologous chromosomes separate during meiosis Each gamete receives 1 copy of each chromosome Law of Independent Assortment Chromosomes separate independently from one another Which copy of each chromosome that ends up in the gamete is random Crossing Over Can occur when the homologous chromosomes overlap during meiosis and swap a segment of DNA

16 Chromosomes fail to separate during meiosis As a result, one gamete receives both of a pair of homologous chromosomes, and the other gets none. Trisomy Results from fertilization of a normal gamete with one that has an extra chromosome due to nondisjunction. Only a few autosomal trisomy syndromes can survive. Monosomy Possible Consequences Types of Nondisjunction Results from fertilization of a normal gamete with one that is missing a chromosome due to nondisjunction. Autosomal monosomy syndromes rarely survive. Spontaneous abortion Decreased lifespan Physical or mental disabilities Autosomal chromosomes Sex chromosomes

17 Meiosis I Nondisjunction Meiosis II Nondisjunction Gametes n + 1 n + 1 n 1 n 1 n + 1 n 1 n Nondisjunction of homologous chromosomes in Meiosis I # chromosomes Nondisjunction of sister chromatids in Meiosis II n

18 DOWN SYNDROME Chromosome Abnormality Symptoms Trisomy 21 Moderate to severe mental retardation Short stature or shortened body parts Characteristic facial features Frequency Approximately 1 out of 800 to 1000 births Most common autosomal trisomy Risk Factors Risk increases with mother s age

19 PATAU SYNDROME Chromosome Abnormality Symptoms Trisomy 13 Many possible physical abnormalities Severe mental retardation Frequency Approximately 1 out of 10,000 to 16,000 births Prognosis It is believed that most cases are spontaneously aborted during pregnancy More than 80% those that survive to birth die in the first month

20 EDWARDS SYNDROME Chromosome Abnormality Symptoms Trisomy 18 Many possible physical abnormalities Severe mental retardation Frequency Second most common autosomal trisomy Approximately 1 out of 3,000 births Prognosis It is believed that most cases are spontaneously aborted during pregnancy Those that are born usually die within days Less than 10% survive more than a year

21 MONOSOMY 21 Chromosome Abnormality Symptoms Monosomy 21 Similar to Down Syndrome (Trisomy 21) Frequency Unknown those with this condition rarely survive to birth Prognosis The only autosomal monosomy known to occasionally survive to birth Those who are born rarely live more than days to weeks

22 KLINEFELTER SYNDROME Chromosome Abnormality Trisomy: XXY Symptoms Male sex organs Abnormally small testes Often have breast enlargement and female contours Usually sterile Frequency Approximately 1 out of 500 male births

23 METAFEMALE (aka TRIPLE-X) Chromosome Abnormality Symptoms Trisomy: XXX Limited fertility Otherwise normal Frequency Approximately 1 out of 1000 female births Risk Factors Risk may increase with age of mother

24 SUPERMALE Chromosome Abnormality Trisomy: XYY Symptoms No obvious physical or medical problems Usually normal sexual development and fertility Normal testosterone and aggression levels Frequency Approximately 1 out of 1000 male births

25 TURNER SYNDROME Chromosome Abnormality Monosomy: XO (only 1 X, no Y) Symptoms Incomplete development of sex organs No effect on intelligence Usually sterile Frequency Approximately 1 out of 2500 female births

26 OY MONOSOMY Chromosome Abnormality Monosomy: OY (no X, only 1 Y) Symptoms Not viable. At least one X chromosome is necessary for life. Frequency Never survives to birth