Cancer cells grow and divide out of control

Cancer Disease caused by the severe disruption of the mechanisms that normally control the cell cycle.

This disruption leads to uncontrolled cell division. Most dangerous characteristic of cancer cells is their ability to spread - Metastasis

Tumors A mass of cells  Benign tumor: an abnormal mass of essentially normal cells  Malignant tumor: masses of cells that result from the reproduction of cancer cells

Normal Uterus

Uterus with Fibroid Tumors

Cancer Treatment There is no “cure” for cancer. Tumors are removed when possible.  Difficult to successfully remove all traces of cancer with surgery.

Cancer Treatment Physicians use radiation and chemotherapy to try to stop the cancer cells from dividing. Can have undesirable side effects in normal body cells.

Radiation Therapy Cancerous tumors are exposed to high-energy radiation. Disrupts cell division. Can often destroy cancer cells with minimal damage to normal cells.

Radiation for Breast Cancer

Chemotherapy Treating the patient with drugs that disrupt cell division. Antimitotic drugs prevent cell division by interfering with the mitotic spindle.

Side effects Radiation can cause damage to the cells of the ovaries or testes, causing sterility. Intestinal cells or hair follicle cells can be affected by chemotherapy, causing nausea or hair loss.

Side effects of Chemotherapy

Meiosis functions in sexual reproduction

Meiosis A type of cell division that produces four cells, each with half the number of chromosomes as the parent cell. Occurs in sex organs – testes and ovaries.

A typical human body cells has 46 chromosomes – 23 pairs. A display of the 46 chromosomes is called a karyotype.

Homologous Chromosomes The two chromosomes of each matching pair  You inherit one chromosome from each pair from your mother and the other from your father.

Homologous Chromosomes Each homologous chromosome in a pair carries the same sequence of genes controlling the same inherited characteristic.  The gene influencing eye color would be located at same location on each chromosome.

Human Chromosomes 23 homologous pairs of chromosomes Sex chromosomes, the 23 rd pair, determine the person’s sex.  X and Y

Diploid and Haploid Cells Diploid cells: contain two homologous sets of chromosomes – almost all human cells.  2n = 46 Haploid cells: cells with a single set of chromosomes, one from each homologous pair.  n = 23

Fertilization: the nucleus of a haploid sperm cell from the father fuses with the nucleus of a haploid egg cell from the mother.  resulting fertilized egg is a zygote.

Fertilization

Meiosis I Homologous chromosomes, each composed of two sister chromatids, are separated from one another.

Meiosis II Sister chromatids are separated, and the resulting cells are haploid (n=23) rather than diploid (2n=46).

Interphase I Cell duplicates its DNA. Each chromosomes then consists of two identical sister chromatids that can be seen more clearly in prophase.

Prophase I Same as prophase, but proteins cause the homologous chromosomes to stick together forming a tetrad. Homologous chromosomes exchange some genetic material – crossing over.

Prophase I

Metaphase I Tetrads move to the middle of the cell and line up across the spindle.

Metaphase I

Anaphase I Homologous chromosomes separate as they migrate to opposite poles. Sister chromatids migrate together.

Anaphase I

Telophase I Chromosomes arrive at the poles Each pole has a haploid daughter nucleus. Only has one set of chromosomes, even though they consist of two sister chromatids. Cytokinesis occurs, forming two haploid daughter cells.

Telophase I

Cytokinesis

Interphase II Chromosomes do not replicate as they do in Interphase I.

Prophase II In each daughter cell, a spindle forms, attaches to the centromeres, and moves the chromosomes to the middle of the cell.

Prophase II

Metaphase II Chromosomes line up at the equator, with spindle fibers attached to each sister chromatid.

Anaphase II Sister chromatids separate and move to opposite poles.

Telophase II Chromatids, now individual chromosomes, arrive at the poles. Cytokinesis splits the cell one more time. End with 4 haploid daughter cells.

Cytokinesis