Transcript meiosis ppt
Meiosis Terms you need to know • Zygote: The fusion of sperm and egg. • Gamete: A mature male (sperm) or female (egg) germ cell that is able to unite with another of the opposite sex to form a zygote. • Homologous Chromosomes: are chromosome pairs, one from each parent, that are similar in length, gene position and centromere location. Terms you need to know • Synapsis: The fusion of chromosome pairs. • Nuclear Membrane: is a double-layered membrane enclosing the nucleus of a cell that controls what enters and leaves the nucleus. • Microtubules: are thick, strong spirals that help define cell structure and movement. Terms you need to know • Spindle Fibers: the structure that separates the chromosomes into the daughter cells during cell division. • Chromatids: holds the replicated DNA of each individual chromosome, which are joined by a centromere. Meiosis • Meiosis is a special type of cell division that produces gametes with half as many chromosomes. • In sexual reproduction, two parents provide an offspring with an unique gene combination. Each parent gives 1/2 of his/her genes (Chromosomes) to the offspring. Video Clip http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=swf::535: :535::/sites/dl/free/0072437316/120074/bio1 9.swf::Stages%20of%20Meiosis Interphase The cell’s chromosomes have duplicated but are in the form of chromatin. Prophase 1 • Homologous chromosomes pair up and form tetrad Prometaphase • Nucleus dissolves and microtubules attach to centromeres. Metaphase 1 • tetrads of homologous chromosomes become attached to the spindle fibers and move to equator Anaphase 1 • Microtubules of the spindle fiber shorten and pull the chromosomes toward the poles, taking both sister chromatids with them. Telophase 1 • The nuclear membrane reforms around the daughter nuclei. Each daughter nucleus contains two sister chromatids for each chromosome, attached to a common centromere. Prophase 2 • Nuclear envelope breaks down and a new spindle forms. Metaphase 2 • Spindle fibers bind to both sides of the centromere. Anaphase 2 • Spindle fibers contract and the sister chromatids move toward the opposite side. Telophase 2 • Nuclear envelope reforms around the set of daughter chromosomes. Four daughter cells are created with the perfect amount of DNA. Mitosis/Meiosis Activity • Find a partner. Each group of partner will be given a baggie with the steps to Mitosis and Meiosis. • Put the different steps in order specific to the process of either Mitosis or Meiosis. • Don’t use your notes!!! • Once you think you have it, raise your hand for us to check!