Comparing Meiosis and Mitosis How are they similar? How are they different?
Definitions Meiosis A type of cellular reproduction in which the number of chromosomes are reduced by half to create gametes Mitosis A process of asexual reproduction in which the cell divides into two, producing two cells with the same number of chromosomes in each as the parent cell
Purpose Meiosis Mitosis Creates gametes, which enables the organism to reproduce sexually Create new cells for general growth of the organism or to repair/replace damaged cells
In which kind of reproducer? Meiosis Mitosis Only occurs in sexual reproducers Occurs in all living things, regardless of how they reproduce
Comparing Chromosomes Meiosis Mitosis Creates four gametes, each has 1/2 the number of chromosomes as the typical cell in the organism Create two cells, each has the same number of chromosomes as the typical cell in the organism
Product Meiosis Mitosis Sex cells, also called gametes, or sperm and egg cells Duplicate cell to the original; happens for all cells except sex cells
How do chromosomes factor into all this? Remember, you get a set of 23 chromosomes from your mom and a set of 23 from your dad. This gave you a full set of 46 chromosomes, or 23 pair. Remember when we created a karyotype with 23 pair of chromosomes to make a face? All of the genes that were used to make you are on these 23 pair of chromosomes.
How do chromosomes factor into all this? During mitosis, these chromosomes double and then divide so that each daughter cell has an exact copy of the original cell s 23 pair (or 46) chromosomes. Here is an image of the chromosomes doubled... Each new cell will get one of each chromosome.
How do chromosomes factor into all this? This is slightly different in meiosis. The chromosomes line up with their pairs (like they are now, but each pair will be in a line along the center of the cell). One chromosome will go into each side, splitting the pair (not the chromosome itself).
How do chromosomes factor into all this? Meiosis is not over, though! The chromosomes split again so that the end result is four gametes, each has half the number of chromosomes as the original cell. In a human, this will result in one copy of chromosome #1, one copy of #2, #3, etc. or a sex cell with 23 chromosomes. Notice in this example, there are two chromosome in the beginning. They duplicate to be two pair and eventually become gametes with one chromosome each.
Let s explore how to color mitosis... Check your work or color as you move through this slide show.
Mitosis Animation http://www.cellsalive.com/mitosis_js.htm
Let s break down this process... If you have not colored mitosis yet, grab four different markers or colored pencils. You will need one color for each chromosome on the coloring sheet.
Mitosis: Interphase This is what the cell would look like as it gets ready to duplicate. Notice the four colors representing the four different sets of genetic information. This will become four different chromosomes as the cell moves into prophase.
Mitosis: Prophase Chromosomes become visible as the genetic material gets organized to go through mitosis. The chromosomes double, which means 46 pair (or 92) would be in human cells during this phase.
Mitosis: Metaphase Chromosomes line up along the center of the cell. The nucleus is gone. The spindle fibers attach to the chromosomes.
Mitosis: Anaphase The chromosomes split at the centromeres and move away from each other. The centrioles appear to pull each half toward opposite sides of the cell.
Mitosis: Telophase This is when the cell actually splits. Two cells are created that have the same number of chromosomes as the interphase cell; in humans this would be 46 total or 23 pairs.
Let s explore how to color meiosis... Check your work or color as you move through this slide show.
Meiosis Animation http://www.cellsalive.com/meiosis_js.htm
Meiosis: Interphase This is what the cell would Chromosomes from dad #1 (orange) and #2 (purple) Chromosomes from mom #1 (green) and #2 (blue) look like as it gets ready to duplicate. Notice the four colors representing the four different sets of genetic information. This will become four different chromosomes as the cell moves into prophase. In humans, this would become 46.
From mom From dad These are copies of Chromosome #1 Meiosis: Prophase I These are copies of Chromosome #2 Chromosomes are visible and have duplicated themselves to create their stereotypical X- shape. As they get organized, some of the chromosomes cross-over, or share genetic material. Notice the two pairs have swapped some of their genetic material.
Meiosis: Metaphase I These are copies of Chromosome #1 These are copies of Chromosome #2 Chromosomes line up with homologous partner. Notice they have switched some genetic information during cross-over.
Meiosis: Anaphase I These are copies of Chromosome #1 These are copies of Chromosome #2 The pairs split so that each cell will get one copy of each homologous pair. In this example, each new cell will get a #1 and a #2.
Meiosis: Telophase I through Metaphase II The chromosomes line up in the two cells that have split. Notice different sets of genetic information are in the These are copies of Chromosome #1 These are copies of Chromosome #2 two cells. The genetic information still comes form what the parent has to pass along.
Meiosis: Anaphase II though Telophase II Different combinations of the original chromosomes are in each gamete. In humans, there are 2 23 different combinations, or 8,388,608 possibilities! * Notice each gamete has a different combination of genes that all came from the original cell. When the odds of two parents are considered, there are ~70 trillion different possible combinations for their offspring.
Let s try the back! This is the most like the mastery check. Mastery check is 10 multiple choice questions; worth 10 points. There is a built in retake for the mitosis mastery check. If you score higher on this than you did on the original, your original grade will be replaced. Last day to take this will be Thursday, April 30 in class.
Answers to the Back 1. Mitosis and Meiosis 2. Mitosis only 3. The cell is growing; the cell is performing its function for the organism; the cell is getting ready to divide, but not yet dividing.
Answers to the Back 4. If n is the number of chromosomes in a gamete... 2n would represent the number of chromosomes in a cell before mitosis, after mitosis and before meiosis. n would represent the number of chromosomes in a cell after meiosis.
Venn Diagram Mitosis = D, E, H, I Both = A Meiosis = B, C, F, G
Let s try the back! This is the most like the mastery check. Mastery check is 10 multiple choice questions; worth 10 points. There is a built in retake for the mitosis mastery check. If you score higher on this than you did on the original, your original grade will be replaced. Last day to take this will be Thursday, April 30 in class.