Mitosis & Meiosis - Teacher Notes This PPT was revised June 25, This PPT accompanies the Mitosis and Meiosis Foldable. The teacher will discuss the slides; students will listen but take no notes. When you reach the Foldable sections which are indicated by a heading that says Mitosis 1. Definition, etc., the students will begin to take notes by filling in their foldable. Mitosis/Meiosis DNA REPLICATION and CELL DIVISION And Auld Lang Syne Every body cell in an organism must have the same number of chromosomes. Human body cells have 46 (2n diploid) chromosomes. If it doesnt, the cell will not be able to function properly. And Auld Lang Syne Before a cell divides, the number of chromosomes (the DNA) must double. Then each new cell can receive the correct number of chromosomes (DNA). And Auld Lang Syne The DNA replicates - makes an exact copy of itself. Step 1Step 2 Step 3 And Auld Lang Syne Replicated Chromosome when DNA replicates itself, it also replicates the chromosome so that the number of chromosomes also doubles Chromatid - replicated DNA/chromosome still held together at the centromere And Auld Lang Syne DNA replication occurs during interphase in the period known as G2 G2G2 S G2G2 M MITOSIS Now that DNA has replicated, Mitosis can begin. The cell now has two identical sets of DNA/chromosomes. MITOSIS Mitosis is when the nucleus of the cell divides. one nucleus one cell two nucleii two cells identical nucleii identical DNA Parent Cell DNA condenses into chromosomes Chromosomes align on the equator Chromosomes separate Two daughter cells MITOSIS Mitosis Cytokinesis Cytokinesis is the division of the cell. Animal cells: Cleavage (indention in cell membrane) Plant cells: Cell plate formation occurs. Its all about chromosomes! There are 46 in human body cells The number of chromosomes remain constant during Mitosis 46 MITOSIS 1. Definition Mitosis is when the nucleus of the cell divides. one nucleus one cell two nucleii two cells identical nucleii identical DNA MITOSIS 2. Type of Rep. Only one parent cell Daughter cells identical to the parent cell. one nucleus one cell two nucleii two cells identical nucleii identical DNA ? Mitosis 3. Advantages offspring cells are exactly like the parent cell Speed Desirable Characteristics Replacement Mitosis 4. Why Divide? to increase surface area to repair damaged cells to grow Mitosis 5. General human daughter cells from mitosis have 46 chromosomes 46 Mitosis 5. General two daughter cells result from mitosis 46 Mitosis 5. General Somatic cells normal body cells Mitosis 5. General daughter cells from mitosis have a diploid chromosome number (2n) 46 MITOSIS - 6. Drawing Mitosis results in two diploid somatic (body) cells exactly like the parent cell. Parent Cell DNA condenses into chromosomes Chromosomes align on the equator Chromosomes separate Two daughter cells MITOSIS Mitosis Review 1. Is the beginning parent cell diploid or haploid (2n or n)? 2. Are the daughter cells diploid or haploid (2n or n)? More Mitosis Review 3. How many daughter cells are produced? 4. Are the resulting daughter cells different from the parent cell? More Mitosis Review 5. Are the resulting daughter cells different from each other? 6. How many chromosomes are in a human parent cell? 7. How many chromosomes are in a human daughter cell from mitosis? More Mitosis Review 8.What types of cells are produced by mitosis? 9. Why (when) does a cell go through mitosis? What is Meiosis? Meiosis is the formation of gametes (egg or sperm) with a haploid chromosome number, Fertilized Egg Cell What is Meiosis? The fertilized egg (zygote) produced by the sperm uniting with the egg then undergoes mitotic division to make the baby. Fertilized Egg Cell Cell Differentiation New individuals arise from zygote stem cells through cellular differentiation Muscle Cells Stem Cells Skin Cells Nerve Cells Blood Cells Why Meiosis? The gametes must have only half the necessary chromosome number for a species When two gametes unite, the resulting cell must have the exact chromosome number for that species MEIOSIS Meiosis has two divisions Division 1, immediately followed by Division II 1 st Division of Mitosis Paternal Homologs Maternal Homologs Two Daughter Cells 2 nd Division of Mitosis Four Daughter Cells Meiosis Meiosis begins with a diploid parent cell Meiosis ends with four haploid daughter cells Meiosis What differences can be seen with meiosis at this point? Meiosis What differences can be seen with meiosis at this point? Meiosis Diversity Meiosis results in gamete cells unlike the parent cell. Gamete cells have only half the chromosome number. Each of the four gamete haploid cells have a different mix of chromosomes. Meiosis Diversity Additional diversity can occur because of crossing over. Crossing causes parts of one chromosome to trade with another like chromosome.. Certain traits remix. Crossing Over What is happening? How does this affect the individual (offspring)? ABCABC abcabc ABCABC abcabc ABCABC abcabc ABCABC abcabc ABCABC abCabC ABcABc abcabc ABcABc abCabC ABCABC abcabc ABcABc abCabC Crossing Over Click the link for a crossing over animation. med.ac.jp/genet/anm/mimov.gifmed.ac.jp/genet/anm/mimov.gif Meiosis 1. Definition Meiosis is the formation of gametes (egg or sperm) with a haploid (n) chromosome number. Fertilized Egg Cell Meiosis 2. Type of Rep. Produces gamete (sex) cells. Fertilization: two gametes unite forming a fertilized egg called a zygote ? Fertilized Egg Cell Meiosis 3. Advantages Meiosis provides diversity in a species. Meiosis produces haploid daughter cells unlike the parent cell and unlike each other. Meiosis 4. Why divide? Meiosis produces cells with only half the required chromosome number for a species. When two gametes unite, the resulting cell has the correct chromosome number for that species Meiosis 5. General Human gametes produced by meiosis have 23 chromosomes The cells have a haploid number of chromosomes. 23 Meiosis 5. General Four haploid cells result from meiosis Meiosis produces gametes (sex cells). 23 MEIOSIS 6. Drawing Meiosis has two divisions. Meiosis results in four haploid cells unlike the parent cell. MEIOSIS 6. Drawing Meiosis has two divisions Division I, immediately followed by Division II 1 st Division of Mitosis Paternal Homologs Maternal Homologs Two Daughter Cells Four Daughter Cells 2 nd Division of Mitosis Meiosis Review Is the beginning parent cell diploid or haploid (2n or n)? 2. Are the resulting daughter cells diploid or haploid (2n or n)? More Meiosis Review 3. How many daughter cells are produced? 4. Are the resulting daughter cells different from the parent cell? More Meiosis Review 5. Are the resulting daughter cells different from each other? 6. What event causes additional remixing of genes during meiosis? More Meiosis Review 6. How many chromosomes are in a human parent cell? 7. How many chromosomes are in a human meiosis daughter cell? MORE MEIOSIS REVIEW 8. What types of cells are produced by meiosis? Fertilized Egg Cell Still More Meiosis Review Meiosis produces egg & sperm which unite to make a new organism. Lets review Mitosis & Meiosis Comparing Mitosis and Meoisis How many daughter cells are produced? Daughter cells haploid or diploid? Daughter cells like or unlike the parent cell? Produces gametes or somatic cells? Has one division or two divisions? 1 st Division of Mitosis 2 nd Division of Mitosis MEIOSIS MITOSIS Mitosis vs. Meiosis EventMitosisMeiosis Produces 4 cells Produces 2 cells New cells identical New cells different New cells have the same number of chromosomes as parent New cells have fewer chromosomes than parent Mitosis vs. Meiosis EventMitosisMeiosis Beginning cells diploid (2n) Beginning cells haploid (n) Ending cells diploid (2n) Ending cells haploid (n) Produces egg and sperm Produces body cells TRY THIS! Free Write On your own paper compare and contrast mitosis and meiosis. You must continually write for 2 minutes. Works Cited Fertilization - sperm fertilizing egg, (No Date). Wikipedia.com, Retrieved June 20, 2006 from the World Wide Web:Website Copyright Permission: This image is copyrighted. However, the copyright holder has irrevocably released all rights to it, allowing it to be freely reproduced, distributed, transmitted, used, modified, built upon, or otherwise exploited in any way by anyone for any purpose, commercial or non-commercial, with or without attribution of the author, as if in the public domain. copyrighted Biology Curriculum Writing Team. PISD