Chapter 11 How Cells reproduce
Cell Cycle
A series of events from the time a cell forms until its cytoplasm divides. It is the life cycle of the cell. A life cycle is an organized series of events that an organism goes through in its life.
Interphase
It is the interval between two mitotic divisions when a cell grows. During this stage, a cell roughly doubles the number of its cytoplasmic components, and replicates its DNA. The three stages of interphase are G1, S, and G2. G1 has to do with the metabolic activities and cell growth. S deals with DNA synthesis which doubles the DNA. G2 has to do with protein synthesis needed for cell division. Cells spend most of their life in interphase.
Prophase
The first stage of mitosis. The chromosomes become visible with a microscope since they condense. A spindle apparatus begins to extend outward from each of the two centrosomes. A spindle is when mcirotubules assemble and lengthen. One of the two centrosomes moves to the opposite end of the cell. The sister chromatids are attached to the opposite centrosomes.
Metaphase
The phase of mitosis that separates duplicated genetic material carried in the nucleus of a parent cell into two individual daughter cells. The chromosomes are joined at a centromere and are called sister chromatids. The chromosomes are now fully attached to the spindle fibers.
Anaphase
The stage of mitosis when the chromosomes move away from each other to opposite poles of the spindle.
Telophase
The final phase of cell division when the chromatids or chromosomes move to opposite ends of the cell and two nuclei are formed.
Telomeres
Noncoding repeat DNA sequences (repeated thousands of times) found at the ends of eukaryotic chromosomes. When chromosomes contain telomeres that are too short, checkpoint gene products halt the cell cycle and cell death soon follows. Most body cells can divide only a certain number of times, but others can divide indefinitely. There are enzymes called telomerase that reverse telomeres shortening that normally occurs after DNA replication. If animals don't have telomeres, they tend to age prematurely.
Cancer
Cancer cells characteristically express high levels of telomerase. It is a malignant neoplasms that gets progressively worse and is dangerous to a person's health. Cancer cells divide relentlessly and produce tumors or they flood the blood with abnormal cells. Cancers are a large family of diseases that involve abnormal cell growth with the potential to invade or spread to other parts of the body. Cancer causes 15-20% of all deaths in developed countries. Mutations in multiple checkpoint genes are required to transform a normal cell into a malignant one. These mutations can be reduced by not smoking or avoiding too much sun exposure. These cancers can be detected early, and if they are detected early enough, they can be removed.
