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Courtney Dauwalter
Biology I
1st Block (100 mins)
7 July 2008
Objective:
1. The student will summarize the steps of meiosis in the cell cycle (DOK 2, Science 3.g).
2. The student will relate the importance of meiosis to sexual reproduction (DOK 3, Science 3.g).
Materials: writing utensil, paper, meiosis cards, overhead projector, transparencies, YouTube, television, scissors
Do-Now: Quiz: 1) List the steps of mitosis from beginning to end, including as much information as you can about each step. 2) A cell has 46 chromosomes and goes through mitosis, how many chromosomes are in the two daughter cells that are produced?
Set: Go over quiz: P.M.A.T., "Mitosis = Make It Two", one parent cell creates two identical daughter cells. How many chromosomes in each daughter cell? 46.
Through our examination of mitosis, we discovered that cells are produced with 46 chromosomes- each of us is made up of 46 chromosomes that determines our hair color, eye color, face shape, etc. Where do we get these chromosomes from? Do you look exactly like your mother? Exactly like your father? Or a mixture of both? Ask students- who do you look like? I have my mom's eyes, my mom's smile, my dad's nose, my dad's hair... I am a little bit like my mother and a little bit like my father. How is this possible? If we have two cells of 46 chromosomes each, one from my mom and one from my dad, I would end up with a cell of (46 + 46 = 92) chromosomes. Do we have 92 chromosomes? Does the chromosome number ever change? No, always 46. Somehow, by combining my mother's chromosomes and my father's chromosomes, I still end up with just 46 chromosomes. How can this be? This occurs because of a process called meiosis- which produces cells of only 23 chromosomes and is in charge of the formation of sex cells (sperm cells and egg cells) that, when added together creates a cell of (23 + 23 = 46) chromosomes total. Today, our objective is to be able to summarize all the stages of meiosis and relate meiosis to sexual reproduction.
Procedure:
1. Recap cell cycle. Identical, still necessary to have the Interphase for cell growth, DNA replication and cell preparation. Instead of mitosis, however, the cell will go through meiosis.
2. Meiosis overhead- What does meiosis produce? What kinds of cells use it? Why do we need meiosis?
3. Chromosome rearrangement/crossing over overhead. Why do we not look exactly like our brothers and sisters if we came from the same parents? The chromosomes rearrange so that meiosis never uses the same exact chromosomes each time around- thus, two parents can reproduce/have children 4, 5, 6 times, and the offspring/children may not look alike at all. Show YouTube video to help students understand what is actually occurring during "Crossing Over".
4. Verbal recap of meiosis- what are we producing? How? Why?
5. Stages of meiosis- P.M.A.T.C I + P.M.A.T.C II - use overhead, break down stages. Relate to mitosis- similarities in what occurs each stage.
Prophase I = Nuclear membrane disappears
Mitotic spindle forms
DNA condenses/coils into chromosomes
Chromosomes pair together (homologous pairs) to form tetrads.
Crossing over occurs- chromosomes exchange genetic info
Metaphase I = Tetrads line up in middle of cell
Anaphase I = homologous chromosomes get pulled to opposite poles
Telophase I = chromosomes reach opposite ends of cell
Nuclear membrane back
Mitotic spindle disappears
Cytokinesis I = Cytoplasm splits = 2 cells = 46 chromosomes each
Immediately following Meiosis I, the cell goes into Meiosis II:
Prophase II = Nuclear membrane disappears
Mitotic spindle reforms
Metaphase II = Chromosomes line up in middle of cell
Anaphase II = Chromatids separate and move to opposite sides of cell. Chromatids = one strand of the chromosome
Telophase II = Nuclear membrane forms
Mitotic spindle disappears
Cytokinesis II = Cytoplasm splits = 4 cells = 23 chromosomes each
The cell divided TWICE.
6. Verbal recap of stages.
7. Hand out meiosis cards. Student work time: cut up cards, figure out what each stage is and put into order.
8. Do on board together: what is each card showing us? What stage does that represent and how do we know? Call students up to board once the cards are in order- write the stage name, what is happening.
9. Hand out worksheets: student work time, whatever is not completed during class will be homework.
Closure: Verbal recap of stages, why meiosis is used and where it occurs (sex cells). Great. Tomorrow we will do some more hands-on learning with meiosis and begin thinking of how meiosis and mitosis are the same and how they are different.
Assessment:
Objective:
1. The student will summarize the steps of meiosis in the cell cycle (DOK 2, Science 3.g).
Formal:The student will complete a worksheet (M) where they summarize the steps of meiosis in the cell cycle (C). The worksheet will be collected and graded (D).
Informal: The teacher will monitor student progress (M) while they summarize the stages of meiosis (C).
2. The student will relate the importance of meiosis to sexual reproduction (DOK 3, Science 3.g).
Formal: The student will complete a worksheet (M) where they will relate the importance of meiosis to sexual reproduction (C). The worksheet will be collected and graded (D).
Informal: The teacher will monitor student progress (M) during class discussions and work time where the importance of meiosis in sexual reproduction is discussed (C).
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