GENERAL BIOLOGY 1 Cell Cycle and Cell Division Everlita E. Canalita (MSU-Iligan Institute of Technology) Michael T. Ruelo (Capitol University) Time Frame: 3 meetings I. Content Standard: The learners demonstrate understanding on cell cycle and cell division. II. Performance Standard: The learners should differentiate mitosis from meiosis. III. Learning Competencies: 1) Describe the stages of mitosis and meiosis given 2n = 6 2) Illustrate the stages of mitosis. 3) Discuss the significance of crossing over and recombination in meiosis in terms of diversity. 4) Explain the significance or application of mitosis and meiosis. IV. Learning Resources: Mitosis: Student Activity Lesson Plan http://faculty.uoit.ca/kay/res/lo/S9_Mitosis.pdf Cell Learning Activity http://www.brighthubeducation.com/middle-school-science-lessons/94267-three-activities-forteaching-cell-cycles/ V. Procedure Mitosis Engage (Get the students’ minds focused on the topic) The teacher will direct the students to make a collage of a small and a big organism using the provided materials (small circles and big circles) Key Points: What do these animals made of? What will happen to these cells when an animal grow? Which of the two animals/plants has more cells? Why do you think this bigger animal has more cells? The teacher will connect the word(s) cell division to cell cycle by telling the students that cell division is only 10% of a cell’s life. Discuss briefly the cycle. Student Activity Collage making activity of a certain organism. Expected Answer: cells Expected Answer: These cells will increase in number Expected Answer: the bigger one Expected Answer: Cells accumulate fats. Cells are able to multiply Or cells are able to divide. Possible skills: Creativity/designing Predicting Critical thinking Explore (Provide students with a common experience) In providing students with a common experience, the teacher will give the students set of straws (3 pairs of different colors and size) Instructions: Divide the set of straws into two (2) equal parts. (Open inquiry) Key Points: How did you separate the straws? What is your basis of dividing the straws in that way? What does the paper box represent? What do the straws represent? Student 2n = 6 Possible skills: Classifying Inferring Predicting Critical thinking 2n = 6 Explain (Teach the concept. Should include interaction between teacher and students The teacher will first group the students (same group as in the explore) and give them picture of each stage of mitosis and interphase (1 picture per group). Instructions: Describe the cell model according to the following criteria: Chromatin/chromosomes Nuclear envelop Pair of centrioles Cell membrane The discussion will focus on the 4 phases of the Mitosis which are the Prophase, Metaphase, Anaphase and Telophase or simply the PMAT and the interphase. Let each group present and describe their cell model and the teacher will only enhance their discussion. P.S. allow the audience classmates to add on if necessary. Mnemonic device: I – Interval (interval between in the cell cycle between two cell divisions P – Prominent (chromosomes) M – Middle (chromosomes) A – Away (chromosomes) T – Two (chromosomes) Cytokinesis – Cleave/Cut (Cell) Student Interphase – nucleus is present Chromosomes appear as thread,dispersed Centrioles are present Nuclear envelop is present and intact Prophase: The chromosomes condense The nuclear envelop starts to disintegrate The centrioles start to separate (P – Prominent) Metaphase: The chromosomes are aligned at the middle Spindle fibers are attached to the chromosomes ( M – Middle) Anaphase: The chromosomes move away from each other going to the opposite poles. (A – Away) Telophase: The chromosomes are now at the opposite sides. The cell starts to divide (cleavage furrow in animals and cell plate in plants) (T – Two) Cytokinesis Possible skills: Communicative Skills/Describing Inferring Critical thinking Collaborative Elaborate (Students apply the information learned in the Explain). The teacher will show a figure showing the union of sperm and egg. Let the students illustrate the stages of mitosis (PMAT) using the given pairs of homologous chromosomes. This time not by group but can be done individually on the board. Student Students output are evaluated through rubric. Possible skills: Inferring Predicting Critical thinking What will happen next? Key points: What will happen to the zygote after fertilization? Illustrate the stages of mitosis that this zygote may undergo? What do you think will happen if the cell will stop dividing? CONTEXTUALIZATION What do you think will happen if the cell will continue to divide beyond its normal division cycle? ( cell will divide 50 times only) CONTEXTUALIZATION Meiosis Engage (Get the students’ minds focused on the topic) The teacher will throw a question on how are sperm cells and egg cells produced. The teacher will give them the idea of spermatogenesis and oogenesis Possible skills: Communicative skills/ Inferring Predicting Critical thinking Explore (Provide students with a common experience) In this phase the teacher will group the students and give them one set of drinking straws inside a paper box. Instruct them to divide the set of straws equally into four. Key Points: What happen to the number of straws after the division? Do you have similar combinations of straws per container? What are the combinations do you have? Possible skills: Classifying Inferring Predicting Student Critical thinking Explain (Teach the concept) The teacher will first group the students (8 groups: for PMAT 1 and PMAT 2) and give them picture of each stage of meiosis I and meiosis II (1 picture per group). Do not forget to include the cytokinesis stage. Instructions: Describe the cell model according to the following criteria: chromosomes Nuclear envelop Pair of centrioles Cell membrane The discussion will focus on the PMAT 1 and PMAT 2 of meiosis. Let each group present and describe their cell model and the teacher will only enhance their discussion. P.S. allow the audience classmates to add on if necessary. Possible skills: Communicative Skills/Describing Inferring Critical thinking Elaborate (Students apply the information learned in the Student Explain). In this phase the students will identify the possible combinations of the chromosomes given. Answer: 1)Prophase 1 (because I see chromosomes in crossing over) Key Questions: What stage of meiosis is shown in the drawing? Why do you say so? What if this prophase will undergo first meiotic division, what are the possible color combinations in each cell? Can you think of other combination aside from this two? What will happen if chromosomes in anaphase 1 and anaphase 2 will not separate? Possible skills: Predicting Communicative Skills/Describing Inferring Critical thinking (deepening the concept) The teacher can discuss a little about chromosomal disorders like monosomy (turners syndrome) and trisomy (down syndrome)cases CONTEXTUALIZATION Evaluate both for Mitosis and Meiosis 1) Arrange the following stages of mitosis and meiosis in order. 2) Compare mitosis and meiosis using the gien table. Mitosis Meiosis Type of cell where it occur No. of daughter cells No. of division(s) No. of chromosomes per daughter cell Purpose/function 3) Why are identical twins look similar? 4) Why are fraternal twins look different? Possible skills: Predicting Communicative Skills/Describing Inferring Critical thinking