Cell Cycle & Mitosis Biology

Chromosomes The growth and development of your cells are carefully controlled by a set of instructions found inside the cell nucleus. These instructions are encoded in DNA and determines that you are human. When cells divide, this material is tightly compacted, creating bodies of DNA and protein called chromosomes.

Chromatids Each chromosome has two identical rods. One is an exact copy of the other. Each identical rod is called a chromatid. The two chromatids are held together by a centromere.

Chromosome Number A set of chromosomes is called a karyotype. Every person has 46 chromosomes, or 23 pairs of chromosomes in a karyotype. When a human cell contains 23 pairs of chromosomes, it is called diploid. Gametes (eggs and sperm) only contain one copy of each chromosome, they are called haploid.

Sex Chromosomes Sex chromosomes determine whether or not you are male or female. They are designated as x or y. If you are female, you have two x chromosomes. If you are male, you have one x and one y chromosome.

Mitosis and Cell Division When a cell reaches a certain size, it will either stop growing or divide. If a cell is to divide and produce two new healthy cells, it must first copy the genetic information in order to function.

Stage 1: Interphase Interphase is the period before cell division begins. During interphase, the cell grows, makes a copy of its DNA, makes copies of the organelles, and gets ready to divide.

Stage 2: Mitosis Eukaryotic cells divide via Mitosis. Mitosis is the process by which the nucleus of a eukaryotic cell divides to form two nuclei, each containing a complete set of the cell’s chromosomes. Mitosis can be broken down into four distinct phases: prophase, metaphase, anaphase, and telophase.

Prophase Prophase is the first and longest phase of mitosis. The chromatin condenses into chromosomes. The centrioles separate, and a spindle begins to form. The nuclear envelope breaks down.

Metaphase The second phase of mitosis, often lasts only a few minutes. Chromosomes line up across the middle of the cell. Spindle fibers begin to form.

Anaphase Third phase of mitosis. Chromosomes begin to pull apart and separate to opposite ends of the cell.

Telophase The fourth and final phase of mitosis. A nuclear membrane re-forms around each cluster of chromosomes. Mitosis is complete.

The Cell Cycle The cycle of growth and division. Mitosis is followed by cell division, also called cytokinesis. http://www.cellsalive.com/mitosis.htm

Cancer and Mutations Cancer arises from a mutated gene that causes a faulty cell cycle. Cancer is a term used to describe a disease characterized by uncontrolled cell division and growth. The result is a clump of cells called a tumor.