cell division
KEY POINTS
- Mitosis is division of the nucleus into two genetically identical daughter nuclei.
- Chromosomes condense by supercoiling during mitosis.
- Cytokinesis occurs after mitosis and is different in plant and animal cells.
- Interphase is a very active phase of the cell cycle with many processes occurring in the nucleus and cytoplasm.
- Cyclins are involved in the control of the cell cycle.
- Mutagens, oncogenes and metastasis are involved in the development of primary and secondary tumors.
Why cells divide?
•Large cells have a reduced SA:Vol ratio
•Growth of organism
•Replace dead, damaged or infected cells
•Asexual reproduction
•Growth of organism
•Replace dead, damaged or infected cells
•Asexual reproduction
stages of the cell cycle
•interphase
–G1: growth, protein synthesis, increase in the number of mitochondria and/or chloroplasts
–S: DNA replication
–G2: growth, protein synthesis, preparation for mitosis/cytokinesis
•mitosis = nuclear division
–prophase
–metaphase
–anaphase
–telophase
•cytokinesis = cellular division
-TERMS:
•Chromosome = DNA + proteins
•Chromatid = one of two copies of DNA
•Sister chromatids = two identical copies of DNA
•Centromere = region on chromosome that joins sister chromatids
•Spindle fiber = microtubules that move chromosomes during cell division
•Centriole = microtubule organizing center
–G1: growth, protein synthesis, increase in the number of mitochondria and/or chloroplasts
–S: DNA replication
–G2: growth, protein synthesis, preparation for mitosis/cytokinesis
•mitosis = nuclear division
–prophase
–metaphase
–anaphase
–telophase
•cytokinesis = cellular division
-TERMS:
•Chromosome = DNA + proteins
•Chromatid = one of two copies of DNA
•Sister chromatids = two identical copies of DNA
•Centromere = region on chromosome that joins sister chromatids
•Spindle fiber = microtubules that move chromosomes during cell division
•Centriole = microtubule organizing center
mitosis
Mitosis is a nuclear division it produces two identical daughter cells during interphase, prophase, metaphase, anaphase, and telophase.
note: In children mitosis occurs very often given that they are growing every day, which means that cells are being reproduced
note: In children mitosis occurs very often given that they are growing every day, which means that cells are being reproduced
interphase
It prepares the cell for mitosis. Chromosomes are not clearly discerned in the nucleus, although a dark spot called the nucleolus may be visible. The cell may contain a pair of centrioles both of which are organizational sites for microtubules.
the interphase has 3 more stages:
prophase
Chromatin in the nucleus begins to condense and becomes visible in the light microscope as chromosomes. The nucleolus disappears. Centrioles begin moving to opposite ends of the cell and fibers extend from the centromeres. Some fibers cross the cell to form the mitotic spindle.
metaphase
Spindle fibers align the chromosomes along the middle of the cell nucleus. This line is referred to as the metaphase plate. This organization helps to ensure that in the next phase, when the chromosomes are separated, each new nucleus will receive one copy of each chromosome.
anaphase
The paired chromosomes separate at the kinetochores and move to opposite sides of the cell. Motion results from a combination of kinetochore movement along the spindle microtubules and through the physical interaction of polar microtubules.
telophase
Chromatids arrive at opposite poles of cell, and new membranes form around the daughter nuclei. The chromosomes disperse and are no longer visible under the light microscope. The spindle fibers disperse, and cytokinesis or the partitioning of the cell may also begin during this stage.
source: http://www.biology.arizona.edu/cell_bio/tutorials/cell_cycle/cells3.html
Mutations and Cancer
•Mutation = random changes to the base sequence of genes
–A mutation may change a proto-oncogene (produces normal cell cycle control) to a oncogene (produces uncontrolled cell cycling)
•Mutagens = agents that produce changes in genes involved in controlling the cell cycle, causing uncontrolled cell division.
for example: -Chemical (asbestos, dioxins, tobacco smoke, etc.)
-X-rays or short-wave UV light
•Metastasis = movement of cells from a primary tumor to set up secondary tumors in other parts of the body.
•Cancer: Cancer is a class of diseases characterized by out-of-control cell growth. There are over 100 different types of cancer, and each is classified by the type of cell that is initially affected.
- A cancerous cell manages to move throughout the body using the blood or lymph systems, destroying healthy tissue in a process called invasion
- That cell manages to divide and grow, making new blood vessels to feed itself in a process called angiogenesis.
source: http://www.medicalnewstoday.com/info/cancer-oncology/
Theory of knowledge:
- A number of scientific discoveries are claimed to be incidental or serendipitous. To what extent might some of these scientific discoveries be the result of intuition rather than luck?