A basic overview of meiosis (production of sex cells)
Meiosis is a two-part cell division process in organisms that sexually reproduce. Meiosis produces gametes with one half the number of chromosomes as the parent cell. The two stages of meiosis are meiosis I and meiosis II. Under normal conditions, chromosomes, (the term for a molecule of DNA ) are packed together in the nucleus. At the end of the meiotic process, four daughter cells are produced. Each of the resulting daughter cells has one half of the number of chromosomes as the parent cell.
Meiosis takes place in reproductive tissue. In animals, meiosis takes place in the testes and in females within the ovaries. In plants, meiosis occurs in the anthers to form pollen grains and within the ovules of the ovaries. In meiosis a diploid cell divides in such a way so as to produce four haploid cells. The haploid cells then form as gametes. Each gamete is genetically different, as a result of both random alignment of the homologous pairs of chromosomes (independent assortment of the chromosomes) and crossing over between members of a homologous pair.
In the first initial stage the chromosomes become visible with a light microscope as they condense ( as they shorten, coil, and thicken). Also, the spindle fibre begins to extend outward from each of the two centriole pairs. Then the nuclear membrane begins to break up and disappear and the chromosomes migrate to the equator, with the homologous chromosomes together One member of each homologous pair then is pulled by spindle fibres to each pole.
The second stage of meiosis continues this process again to split the separated homozygous chromosomes into four gametes The cell then divides into two and the nuclear membrane may reform, although it does not always happen. The centrioles then move back to the opposite poles and they are split apart by spindle fibres, creating four different gametes for reproduction.
The process whereby one or more gene alleles present in one chromosome may be exchanged with their alternative alleles on a homologous chromosome to produce a recombinant (crossover) chromosome. This may happen when in the first stage of meiosis when homologous chromosomes line up with each other on the equator to be separated by spindle fibres. This helps contribute further to variation and it is at this stage that gene mutations can occur.
Please do not pass this sample essay as your own, otherwise you will be accused of plagiarism. Our writers can write any custom essay for you!
Cellular Respiration Cellular Reproduction is the process by which all living things produce new organisms similar or identical to themselves. This has to happen because if a species were not able to reproduce, that species would quickly become extinct. Reproduction consists of a basic pattern: the conversion by a parent organism of raw materials into offspring or Biology Cell Parts Sample essay topic, essay writing: Biology Cell Parts - 1344 words
Nucleus - "the brain" or control center of the cell. The Nucleus, a membrane-bound structure of a cell, plays two crucial roles in controlling the cell. The nucleus carries the cell's genetic information that determines if the organism will develop, for instance, into a tree Gregor Mendels Theories Of Genetic Inheritance Sample essay topic, essay writing: Gregor Mendels Theories Of Genetic Inheritance - 313 words
Gregor Mendel's Theories of Genetic InheritanceGregor Mendel played a huge role in the underlying principles of geneticinheritance. He grew up in a Augustinian brotherhood where he learnedagricultural training with basic education. He then went on to the OlmutzPhilisophical Institute and then entered Breeding Roses (this comes in handy for biology if your studying plants and need some extra credit) Every rose breeder has certain more or less definite ideals or objectives toward which his breeding efforts are directed. Some of these ideals are shared by all rosarians, while others express the individuality of the breeder and may or may not find popular acceptance. Thus in my opinion an ideal red rose, for example, should Cell Organelle Overview The studies of Robert Hooke 1665 into a plant material would allow the determination of a pore like regular structure surrounded by a wall of which he called ‘cells’ this in itself unbeknownst to him, was the discovery of the fundamental unit of all living things.
In 1838 a botanist called Schleiden derived the theory ‘The
Need Book Reports, essays, lectures? Save to bookmarks - » A basic overview of meiosis (production of sex cells). Collections of essays on literature!