Topic 3B.2 Mitosis

prophase

the first stage of active cell division where the chromosomes are coiled up and consist of two daughter chromatids joined by the centromere; the nucleolus breaks down

metaphase

the second stage of active cell division where the spindle of overlapping protein microtubules forms and the chromatids line up on the metaphase plate

anaphase

the third stage of active cell division where the centromeres split so chromatids become new chromosomes; they are moved to the opposite poles of the cell, centromere first, by contractions of the microtubules of the spindle

telophase

the fourth stage of active cell division where a nuclear membrane forms around the two sets of chromosomes, the chromosomes unravel and the spindle breaks down

centromere

the region where a pair of chromatids are joined and which attaches to a single strand of the spindle structure at metaphase

metaphase plate (equator)

the region of the spindle in the middle of the cell along which the chromatids line up

clones

genetically identical individuals resulting from asexual reproduction in a single parent

mitotic index

the ratio between the number of cells in a tissue sample that are in mitosis and the total number of cells in the sample