meiotic divisions is called interkinesis which is short-lived. Meiosis II – Equational division. This division is otherwise called mitotic meiosis because it resembles mitosis. Since it includes all the stages of mitotic divisions.
Prophase II The chromosome with chromatids becomes short, condensed, thick and becomes visible. New spindle develops at right angles to the cell axis. Nuclear membrane and nucleolus disappear. Metaphase II Chromosome arranged at the equatorial plane of the spindle.
Microtubules of spindle gets attached to the centromere of sister chromatids. Anaphase II Sister chromatids separate. The daughter chromosomes move to the opposite poles due to shortening of spindle fibres. Centromere of each chromosome split, allowing to move towards opposite poles of the cells holding the sister chromatids.
Telophase II Four groups of chromosomes are organised into four haploid nuclei. The spindle disappears. Nuclear envelope, nucleolus reappear. After karyokinesis, cytokinesis follows and four haploid daughter cells are formed, called tetrads .
. . Significance of Meiosis • This maintains a definite constant number of chromosomes in organisms. • Crossing over takes place and exchange of genetic material leads to variations among species.
These variations are the raw materials to evolution. Meiosis leads to genetic variability by partitioning different combinations of genes into gametes through independent assortment. • Adaptation of organisms to various environmental stress. Table .
: Difference between mitosis in Plants and Animals Plants Animals Centrioles are absent Centrioles are present Asters are not formed Asters are formed Cell division involves the formation of a cell plate Cell division involves furrowing and cleavage of cytoplasm Occurs mainly at meristem Occurs in tissues throughout the body Figure . : Meiosis Table . : Difference Between Mitosis and Meiosis (Figure . ) Mitosis Meiosis One division Two divisions Number of chromosome remain the same Number of chromosomes is halved Homologous chromosomes line up separately on the metaphase plate Homologous chromosomes line up in pairs at the metaphase plate Homologous chromosome do not pair up Homologous chromosome pairup to form bivalent Chiasmata do not form and crossing over never occurs Chiasmata form and crossingover occurs Daughter cells are