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 * Mitosis and Meiosis **

By: Alex Brooks and Erica Green
====Mitosis is the process in cell division by which the nucleus divides, typically consisting of four stages, prophase, metaphase, anaphase, and telophase, and normally resulting in two new nuclei, each of which contains a complete copy of the parental chromosomes. ==== - Longest phase of the cell cycle 1. Gapl- rapid growth and development 2. Synthesis- replicaiting DNA 3. Gap 2- prep for mitosis 4. 90% time in Interphase 5. DNA in chromotin form
 * __Interphase__**

- Longest phase of mitosis 1. DNA species 2. Nuclear envelope disolves 3. Chromosomes appear
 * __Prophase__**

1. Spindles form 2. Chromosomes move to the middle
 * __Metaphase__**

1. Centromere divides 2. Sister chromatides are pulled to opposite poles
 * __Anaphase__**

1. Nuclear envelope reforms 2. DNA is uncoiling 3. Cytokinesis occurs
 * __Telephase__**

Key Terms on Mitosis:
 * Allele- An alternative form of a [|gene] (one member of a pair) that is located at a specific position on a specific [|chromosome].
 * Centrioles- Found in animal cells and help to organize the assembly of microtubules during cell division. Centrioles replicate during the [|interphase] stage of [|mitosis] and ﻿ [|meiosis] ﻿.
 * Centromere- A region on a chromosome that joins two sister chromatins. In [|prophase] of [|mitosis], specialized regions on centromeres called ﻿ [|kinetochores] ﻿ attach chromosomes to spindle [|polar fibers] . These fibers help to manipulate and separate chromosomes during cell division.
 * Chromatid- Is one-half of a replicated chromosome.
 * Chromatin- Mass of genetic material composed of [|DNA] and proteins that condense to form [|chromosomes] during eukaryotic cell division.
 * Chromosome- Criss cross design of genes that carries heredity information.
 * Cytokinesis- Division of the cytoplasm that produces distinct daughter cells.

More key terms click on this website http://biology.about.com/od/biologydictionary/a/mitosisgloss.htm

Mitosis video- []
=== Meiosis is the process of two consecutive nuclear divisions in the formation for germ cells in animals and of spores in most plants, by which the number of chromosomes ordinarily are reduced from the diploid, or double, number found in somatic cells to the haploid, or halved, number found in gametes and in spores. ===


 * Numbers || Meiosis || Mitosis ||
 * 1 || Meiosis takes place within gamete cells (sex cells). || Mitosis takes place within somatic cells (cells that make up the body). ||
 * 2 || Two divisions of the mother cell result in four meiotic products or haploid gametes. || One single division of the mother cell results in two daughter cells. ||
 * 3 || A meiotic mother cell is always diploid. || A mitotic mother cell can either be haploid or diploid. ||
 * 4 || The meiotic products contain a haploid (n) number of chromosomes in contrast to the (2n) number of chromosomes in mother cell. || The number of chromosomes per nucleus remains the same after division. ||
 * 5 || The centromeres do separate during anaphase II, but not during anaphase || The centromeres split during anaphase ||

> **-S phase: the period during which DNA is synthesized** > **-G2 phase: the period after DNA synthesis has occurred but prior to the start of prophase.** > -The pairs of homologous chromosomes (the bivalents), now as tightly coiled and condensed as they will be in meiosis, become arranged on a plane equidistant from the poles called the metaphase plate. > -Spindle fibers from one pole of the cell attach to one chromosome of each pair seen as sister chromatids, and spindle fibers from the opposite pole attach to the homologous chromosome again, seen as sister chromatids. > > > >
 * ==[[image:http://www.ba-education.com/dna/meiosis.jpg width="326" height="691" align="left"]] Interphase==
 * **-is composed of three phases**
 * **-G1 phase: the period prior to the synthesis of DNA.**
 * ==**Prophase**==
 * **-The chromosomes become visible**
 * **-The two chromosomes combine or synapse to form tetrads**
 * **-At this point the chromosomes cross over at points called chiasmata**
 * **-Crossing over allows the chromosomes to exchange genetic material, allowing for more different combinations of genetic materia**
 * **-The nuclear envelope disperses**
 * **-The spindle moves into the center, and the tetrads become connected to the spindle fibers by kinetochores.**
 * ==**Prometaphase**==
 * **-The nuclear envelope breaks down, allowing microtubule access to chromosomes**
 * **metaphase 1**
 * - The centrioles are at opposite poles of the cell.
 * ==Anaphase==
 * **-chromosomes move to opposite poles of the cell**
 * **-when the two chromosomes of each bivalent (tetrad) separate and start moving toward opposite poles of the cell as a result of the action of the spindle.**