Chapter 10

10.3 Regulating the Cell Cycle A. Tumors 1. Caused by cell reproduction that is out of control 2. Creates a mass of cells 3. If the cells are normal, then the tumor is called benign

4. Cell of a benign tumor always stay in the original site in the body 5. Benign tumors can cause problems a. Put pressure on vital organs because space is limited in the body b. Can usually be completely removed by surgery

6. Masses of cells that come from cancerous cells are called malignant tumors a. Very dangerous b/c cancerous cells have the ability to spread to different locations of the body or metastasize

MRI of a Brain Tumor that metastasized from the lung.

CT Scan of a Bone Tumor

7. What causes cancer? a. Many cancerous cells have a defect in the p53 gene b. P53 gene normally halts mitosis until all DNA is replicated c. Damaged p53 genes cause cells to lose the information needed to respond to signals that control their growth

B. Controls of Cell Division 1. Rate of cell division increases due to injury 2. Rate of cell division decreases when the healing is complete 3. Regulatory Proteins a. Cyclins: Proteins that regulates the cell cycle b. Tells eukaryotic cells when to divide c. The cell cycle is controlled by internal & external regulatory proteins

 Internal regulators  Respond to events occurring inside the cell  Ex. The cell will not enter mitosis until all the DNA has been copied  Ex. The cell will not enter anaphase unless all the spindle fibers are attached to the centromeres  External Regulators  Respond to events outside the cell  Tells cell to speed up or slow down the cell cycle  Ex. Growth factors are released by cells to stimulate other cells to divide

4. Apoptosis a. Programmed cell death b. The cell will self –destruct c. Happens when cell is damaged d. Key role in development of an embryo - Ex. Gets rid of the webbing between fingers & toes of embryo e. AIDS & Parkinson’s- too much apoptosis occurs

11.4 Meiosis A. Homologous Chromosomes 1. Chromosomes in the cell have a “twin” that is similar in size, shape and sequence of genes that control the same inherited traits a. the pair of twin chromosomes are called homologous chromosomes b. humans have 23 pairs of homologous chromosomes

2. One is inherited from your mother and one from your father 3. If we view the chromosomes on a karyotype, we see the chromosomes paired and in order from largest to smallest. a. Pair #1- largest, pair #23- sex chromosomes (XX- female) or (XY- male) X- female, Y Male

B. Diploid and Haploid Cells 1. All human body cells or somatic cells are diploid 2n = Sex cells or gametes are haploid n = During fertilization, the sperm cell fertilizes an egg cell and creates a zygote. a. The zygote is diploid

C. Meiosis vs. Mitosis MitosisMeiosis Produces 2 diploid cellsProduces 4 haploid daughter cells Offspring cells are identical to the parent Involves the exchange of genetic material between homologous chromosomes Involves 1 divisionInvolves 2 divisions 4 stages: PMAT8 stages: PMAT x 2

D. 2 Meiotic Divisions 1. Meiosis I a. Interphase- G1  S  G2 b. Prophase I- homologous chromosomes pair up and form a tetrad, crossing over occurs between the homologous chromosomes c. Metaphase I- same as mitosis d. Anaphase I- homologous chromosomes separate e. Telophase I and Cytokinesis- same as mitosis, the 2 new cells are haploid

2. Meiosis II a. Prophase II- same as mitosis b. Metaphase II- same as mitosis c. Anaphase II- sister chromatids separate d. Telophase II and Cytokinesis- same as mitosis except now there are 4 haploid cells 3. Reminder: a. Law of Independent assortment- metaphase I b. Law of segregation- Anaphase