Prophase | Health Encyclopedia: Prophase

Prophase: From 1 Different Sources

n. the first stage of *mitosis and of each division of *meiosis, in which the chromosomes become visible under the microscope. The first prophase of meiosis occurs in five stages (see leptotene; zygotene; pachytene; diplotene; diakinesis).

Health Source: Oxford | Concise Colour Medical Dictionary
Author: Jonathan Law, Elizabeth Martin

Chiasma

n. (pl. chiasmata) (in genetics) the point at which homologous chromosomes remain in contact after they have started to separate in the first division of *meiosis. Chiasmata occur from the end of prophase to anaphase and represent the point at which mutual exchange of genetic material takes place (see crossing over).... chiasma

Chromatid

n. one of the two threadlike strands formed by longitudinal division of a chromosome during *mitosis and *meiosis. They remain attached at the *centromere. Chromatids can be seen between early prophase and metaphase in mitosis and between diplotene and the second metaphase of meiosis, after which they divide at the centromere to form daughter chromosomes.... chromatid

Diakinesis

n. the final stage in the first prophase of *meiosis, in which homologous chromosomes, between which crossing over has occurred, are ready to separate.... diakinesis

Diplotene

n. the fourth stage in the first prophase of *meiosis, in which *crossing over occurs between the paired chromatids of homologous chromosomes, which then begin to separate.... diplotene

Leptotene

n. the first stage in the first prophase of *meiosis, in which the chromosomes become visible as single long threads.... leptotene

Meiosis

(reduction division) n. a type of cell division that produces four daughter cells, each having half the number of chromosomes of the original cell. It occurs before the formation of sperm and ova and the normal (*diploid) number of chromosomes is restored after fertilization. Meiosis also produces genetic variation in the daughter cells, brought about by the process of *crossing over. Meiosis consists of two successive divisions, each divided into four stages (see prophase; metaphase; anaphase; telophase). (See illustration.) Compare mitosis. —meiotic adj.... meiosis

Mitosis

n. a type of cell division in which a single cell produces two genetically identical daughter cells. It is the way in which new body cells are produced for both growth and repair. Division of the nucleus (karyokinesis) takes place in four stages (see prophase; metaphase; anaphase; telophase) and is followed by division of the cytoplasm (cytokinesis) to form the two daughter cells (see illustration overleaf). Compare meiosis. —mitotic adj.... mitosis