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Introduction


Meiosis is an important biological concept that all students should know and understand. Its basic function is important for genetic diversity and the continuation of life in all plants and animals. This tutorial was made to help simplify a somewhat confusing, but important process. Below is the AP Biology Laboratory Manual's Introduction to meiosis (p. 27).

" Meiosis reduces the chromosome number in half during the formation of gametes in animals and spores in plants. During the first meiotic "reduction division," the chromosomal pairs are partitioned so that each gamete (or spore) contains one of each chromosomal pair, i.e., it is haploid. When haploid gametes unite during fertilization, the resulting zygote is diploid, having received one chromosome of each pair from each parent.

Meiosis involves two successive nuclear divisions that produce four haploid cells. The first division (meiosis I) is the reduction division; the second division (meiosis II) separates the chromatids.

Mitotic cell division produces new cells genetically identical to the parent cell. Meiosis increases genetic variation in the population. Each diploid cell undergoing meiosis can produce 2ⁿ different chromosomal combinations, where n is the haploid number. In humans the number is 2²³ which is more than eight million different combinations. In addition, the variation increases dramatically because during meiosis I, each pair of chromosomes (homologous chromosomes) comes together in a process known as synapsis. Chromatids of homologous chromosomes may exchange parts in a process called crossing over. You can estimate the relative distance between two genes on a given chromosome by calculating the percentage of crossing over that takes place between them. "

This tutorial will go over each step of meiosis and the explanations will be enhanced with actual cell pictures and 3D animations. There will also be links within the text that leads to additional information relating to meiosis. At the bottom of each screen, there will be forward and backward links to the proceeding and preceding step. Also the side menu will allow the user access to any step without going through the whole meiosis sequence. Click here to get started!