Mitosis Meiosis
Mitosis and Meiosis
I. These two processes function to pass chromosomes from one cellular generation to the next in a very carefully controlled manner. II. Mitosis and Meiosis are both correctly described as nuclear division; they are never correctly called cell division, or any kind of reproduction. It is possible (and often quite normal) for nuclei to divide when cells don't. And organisms reproduce; nuclei and cells divide.
III. Mitosis A. Mitosis is the division of a nucleus to produce two genetically identical daughter nuclei. B. Mitosis is utilized for any function which requires the production of more cells with identical genetic information. These processes include the vase majority of cell production during the growth of an organism, the cell division needed for healing and repair, and the division of nuclei when an organism is in the process of asexual reproduction. Note: Mitosis is not asexual reproduction, nor can it be called asexual cell (or even nuclear) division. C. Because the vast majority of the cells in a multicellular organism were produced by mitotic cell division, those cells all have identical nuclei. They obviously don't all look or function alike. Cells mature through a process called differentiation in which select sets of genes are turned on and off, resulting in changes in the structure and function of the cell. IV. Meiosis A. Meiosis is the division of one diploid (usually) nucleus to produce four haploid (usually) nuclei, all genetically different. Though the vast majority of the time the chromosome number reduction is from diploid to haploid, in some cases it may be from, say, hexaploid (eg., wheat) to triploid. B. Meiosis performs a key task necessary in a sexual life cycle. Since fertilization (which is the actual sexual event in the life cycle) automatically doubles chromosome number by combining the chromosomes of an egg and a sperm, it is essential that some event occur somewhere in
I. These two processes function to pass chromosomes from one cellular generation to the next in a very carefully controlled manner. II. Mitosis and Meiosis are both correctly described as nuclear division; they are never correctly called cell division, or any kind of reproduction. It is possible (and often quite normal) for nuclei to divide when cells don't. And organisms reproduce; nuclei and cells divide.
III. Mitosis A. Mitosis is the division of a nucleus to produce two genetically identical daughter nuclei. B. Mitosis is utilized for any function which requires the production of more cells with identical genetic information. These processes include the vase majority of cell production during the growth of an organism, the cell division needed for healing and repair, and the division of nuclei when an organism is in the process of asexual reproduction. Note: Mitosis is not asexual reproduction, nor can it be called asexual cell (or even nuclear) division. C. Because the vast majority of the cells in a multicellular organism were produced by mitotic cell division, those cells all have identical nuclei. They obviously don't all look or function alike. Cells mature through a process called differentiation in which select sets of genes are turned on and off, resulting in changes in the structure and function of the cell. IV. Meiosis A. Meiosis is the division of one diploid (usually) nucleus to produce four haploid (usually) nuclei, all genetically different. Though the vast majority of the time the chromosome number reduction is from diploid to haploid, in some cases it may be from, say, hexaploid (eg., wheat) to triploid. B. Meiosis performs a key task necessary in a sexual life cycle. Since fertilization (which is the actual sexual event in the life cycle) automatically doubles chromosome number by combining the chromosomes of an egg and a sperm, it is essential that some event occur somewhere in