Mitosis Stages & Cell Division PDF

# What are the stages of Mitosis? ### The ploidy of a cell refers to its number of sets of chromosomes. * **Diploid:** Two sets of chromosomes * **Haploid:** One set of chromosomes ### During interphase, the chromosome takes on the form of chromatin. * Chromatin is a loose DNA molecule. * There...

# What are the stages of Mitosis? ### The ploidy of a cell refers to its number of sets of chromosomes. * **Diploid:** Two sets of chromosomes * **Haploid:** One set of chromosomes ### During interphase, the chromosome takes on the form of chromatin. * Chromatin is a loose DNA molecule. * There are two sister chromatids in each chromosome. ### Mitosis is known as **equational division**, while meiosis is known as **reductional division**. * Mitosis functions for the **growth, repair, and development** of body cells, also known as **somatic cells**. ## Stages of Mitosis: ### 1. Prophase: * Chromatin fiber condenses into chromosomes. * The nucleolus disappears. * The nuclear membrane may/may not break down. ### 2. Metaphase: * Chromosomes line up in the **center**, known as the **metaphase plate.** * Chromosomes are attached to the spindle fibers by structures called **kinetochores**. ### 3. Anaphase: * Each chromosome is separated into two sister chromatids. * Sister chromatids migrate towards the opposite ends ("poles") of the cell through the centromere. * Each pole receives an equal number of chromatids. ### 4. Telophase: * Chromatids cluster at each pole and start to decondense. * The nuclear membrane reforms to enclose the decondensed chromatids. * Microtubules are broken down in a process called depolymerization. * This state continues until they are needed again. ### Cytokinesis: * The membrane separates to produce two daughter cells. * In animal cells, cytokinesis is characterized by the formation of a **cleavage furrow** (a contraction in the cell membrane) between the daughter cells. * In plant cells, cytokinesis is characterized by the presence of a structure known as a cell plate. ## Cell Division: Mitosis vs. Meiosis * **Mitosis and meiosis** are similar in that they happen after interphase, are relatively short compared to interphase, lead to the production of new daughter cells, and start with a diploid parent cell. ### Mitosis: * Also known as **equational division**. * Parent cell's chromosome number is equal to that of its daughter cells. * Involves a single cell division, which produces two daughter cells. * Function: growth, repair, and development of body cells or somatic cells. ### Meiosis: * Also known as **reductional division**. * Daughter cells will have a reduced number of chromosomes (haploid). * Involves two cell divisions, which produces four daughter cells. * Function: Production of gametes. ## What are the stages of mitosis? * **Target**: * Describe the chromosome and its parts * Differentiate haploid and diploid cells * Illustrate the stages of mitosis * Discuss the importance of mitosis ## Explore: * The teacher will have the class watch a video showing a salamander embryo's development from a single cell. * Afterward, answer the following questions: * How do you think the cells "know" how to divide and position themselves accordingly? * Do think other animal species have a similar process of embryonic development? Why or why not? ## Examine: * Recall from the previous lesson that the M phase of the cell cycle, otherwise known as cell division, can be either mitosis or meiosis. * The two are similar in many ways but have distinct characteristics. ## The Chromosome: * A chromosome is a *tightly-packaged* DNA molecule found in the nucleus * In eukaryotes, it varies in size, structure, and appearance depending on the cell cycle stage. * The chromosome appears as thread-like chromatin during interphase. * Chromatins are threads of *nucleosomes*, which are DNA molecules wrapped around proteins known as histones. * The chromosomes appear as single chromatids during the G1 phase. * After the S phase, the chromatids double, forming two sister chromatids. * These sister chromatids are joined at their *centromeres*. ## Ploidy: * The ploidy level of a cell refers to the number of sets of chromosomes it has. * **Diploid (2N) cells:** Two sets of chromosomes * **Monoploid (N) cells:** One set of chromosomes. A haploid cell is a cell that contains half the set of chromosomes of a diploid organism. All body cells or somatic cells are diploid, while sex cells or gametes are haploid. ## Autosomes and Sex Chromosomes: * **Autosomes:** Also known as body chromosomes, are present in all cells of both males and females of an organism. * **Sex chromosomes:** Differ in each biological sex. Humans have 22 pairs of autosomes and one pair of sex chromosomes. * In males, they are **XY**. * In females, they are **XX**. * The chromosome number of diploid human cells is 2N = 46, while for haploid human cells such as gametes, it is N = 23. ## Euploid and Aneuploid: * **Euploid:** Cells with a complete set of chromosomes. * **Aneuploid:** Cells that have missing or excess chromosomes. * For instance, an extra chromosome 21 in humans will result in Down Syndrome. ## Karyotype: * The two copies of a particular chromosome are called **homologous chromosomes**, which can be seen through a karyotype. * A karyotype is an image that shows all of a specific individual's chromosomes.