W3 - 1ST CELL DIVISION.pptx for grade 7 students

cell division

1. Let’s Pray

2. HOUSE RULES 1. Always observe our health protocols. 2. Turn off your phones. Using of phone during class hours is strictly prohibited. Violation of this rule is an automatic ground for phone confiscation. 3. One speaker at a time. When someone is speaking, keep quiet and listen. If you want to say something, raise your hand and wait for your teacher to recognize you.

3. LEARNING OBJECTIVES: 1 . Identify and discuss what happens during the phases of the cell cycle 2. Recognize that cell reproduce through two types of cell division, mitosis and meiosis, and describe mitosis as cell division for growth and repair 3 . Identify and describe the event taking place in each stage of mitosis 4. Identify and describe the event taking place in each stage of meiosis 5. Explain the genetic information is passed on to offspring from both parents by the process of meiosis and fertilization 6. Compare and contrast the similarities and differences between mitosis and meiosis. 7. Describe the two methods of reproduction exhibited by different kind of organisms 8. Differentiate sexual from asexual reproduction in terms of: a. number of individual involved b. similarities of offspring to parent

4. What do you think happens when your wound heals?

5. Cell Division is a fundamental biological process by which a parent cell divides to produce new cells. It is essential for growth, development, repair of damaged tissues, and reproduction in living organisms.

6. MITOSIS

7. What is mitosis? Mitosis is the process responsible for regeneration and repair. Mitosis helps in cell growth and development. Mitosis is a type of cell division that results in two identical daughter cells .

8. LET’S LOOK AT THE STAGES OF MITOSIS

9. Interphase is the longest and most active stage in the cell cycle, occurring before mitosis begins. . INTERPHASE Interphase prepares the cell for the division process. . The preparation stage in mitosis is interphase which involves the G1 phase, S phase, and G2 phase .

10. Interphase is divided into three phases: G₁ phase (Gap 1): The cell grows in size. It produces proteins and organelles. The cell performs its normal functions. S phase (Synthesis): DNA replication occurs. Each chromosome makes an exact copy of itself (forming sister chromatids). G₂ phase (Gap 2): The cell continues to grow. It prepares all the necessary materials (like spindle fibers) for mitosis. The cell checks for errors in DNA replication.

11. The DNA coils into chromosomes. The nuclear membrane disappears. P ROPHASE

12. Chromosomes align themselves at the M iddle of the equatorial plane. Kinetochore proteins are attached to the centromere of each chromosome. Spindle fibers are fully developed M ETAPHASE

13. Chromatids separate and move to opposite ends o f the cell. A NAPHASE

14. New nuclear membranes form around the two sets of chromosomes. T ELOPHASE

15. final stage of cell division where the cytoplasm of the parent cell is divided into two daughter cells . Cytokinesis

16. ACTIVITY 1.1 CYTOKINESIS ANAPHASE METAPHASE CLASSIFICATION INTERPHASE PROPHASE TELOPHASE 1.___________________ 4.___________________ 6.___________________ 5.___________________ 3.___________________ 2.___________________

17. Mitosis for Growth and Repair Happens in body cells (like skin, bones, or muscles). Purpose: To grow, repair, or replace damaged cells. Makes 2 identical cells (same number of chromosomes as the original). Example: When you get a wound, mitosis helps create new skin cells to heal it.

18. Stages of Mitosis Prophase – The DNA coils into chromosomes. The nuclear membrane disappears. Metaphase – Chromosomes line up in the middle of the cell. Anaphase – Chromosomes are pulled apart to opposite sides. Telophase – New nuclear membranes form around the two sets of chromosomes. Cytokinesis – The cell splits into two identical daughter cells .

19. MEIOSIS

20. What is meiosis? Not all cells divide through the process of mitosis. Organisms that reproduce sexually also undergo a type of cell division called meiosis . Meiosis occurs in sex cells and is similar in process to mitosis.

21. Why is it important? Meiosis makes sure that all organisms produced via sexual reproduction contain the correct number of chromosomes - half from each parent.

22. LET’S LOOK AT THE STAGES OF MEIOSIS

23. The process of meiosis is divided into meiosis I and meiosis II which both have multiple phases. Meiosis I is a type of cell division unique to germ cells, while meiosis II is similar to mitosis.

24. MEIOSIS I

25. The DNA in the cell is copied resulting in two identical full sets of chromosomes. Outside of the nucleus are two centrosomes, each containing a part of centrioles, these structures are critical for the process of cell division. During interphase, microtubules extend from these centrosomes. INTERPHASE

26. The copied chromosomes condense into X-shaped structure that can be easily seen under a microscope. Each chromosome is composed of two sister chromatids containing identical genetic information. The chromosomes pair up so that both copies of chromosome 1 are together, both copies of chromosome 2 are together, and so on. PROPHASE 1

27. The pair of chromosomes may then exchange bits of DNA in a process called recombination or crossing over. At the end of prophase 1, the membrane around the nucleus in the cell dissolves away, releasing the chromosomes. The meiotic spindle, consisting of microtubules and other proteins, extends across the cell between centrioles. PROPHASE 1

28. The chromosome pairs line up next to each other along the center (equator) of the cell. The centrioles are now at opposite poles of the cell with the meiotic spindles extending from them. The meiotic spindle fibers attach to one chromosome of each pair. METAPHASE 1

29. The pair of chromosomes are then pulled apart by the meiotic spindle, which pulls one chromosome to one pole of the cell and the other chromosome to the opposite pole. In meiosis I, the sister chromatids stay together. This is different to what happens in mitosis and meiosis II. ANAPHASE 1

30. The chromosomes complete their move to the opposite poles of the cell. At each pole of the cell a full set of chromosomes gather together. A membrane forms around each set of chromosomes to create two new nuclei. The single cell then pinches in the middle to form two separate daughter cells each containing a full set of chromosomes within a nucleus. This process is known as cytokinesis. TELOPHASE 1 and Cytokinesis

31. MEIOSIS II

32. PROPHASE 2 Now there are two daughter cells, each with 23 chromosomes (23 pairs of chromatids) In each of the two daughter cells the chromosomes condense again into visible X-shaped structures that can be easily seen under a microscope. The membrane around the nucleus in each daughter cell dissolves away releasing the chromosomes. The centrioles duplicate. The meiotic spindle forms again.

33. In each of the two daughter cells, the chromosomes (pair of sister chromatids) line up end-to-end along the equator of the cell. The centrioles are now at opposites poles in each of the daughter cells. Meiotic spindle fibers at each pole of the cell attach to the sister chromatids. METAPHASE 2

34. ANAPHASE 2 The sister chromatids are then pulled to opposite poles due to the action of the meiotic spindle. The separated chromatids are now individual chromosomes.

35. TELOPHASE 2 The chromosomes complete their move to the opposite poles of the cell. At each pole of the cell a full set of chromosomes gather together. A membrane forms around each set of chromosomes to create two new cell nuclei.

36. TELOPHASE 2 This is the last phase of meiosis; however, cell division is not complete without another round of cytokinesis. Once cytokinesis is complete, there are four granddaughter cells, each with half a set of chromosomes (haploid).

37. PROPHASE METAPHASE ANAPHASE THE WHOLE PROCESS TELOPHASE FIRST PHASE SECOND PHASE ANAPHASE TELOPHASE METAPHASE PROPHASE

38. 1.______ 8.______ 7.______ 6.______ 5.______ 4.______ 3.______ 2.______

39. Quick Recap Time!

40. Mitosis for Growth and Repair Happens in body cells (like skin, bones, or muscles). Purpose: To grow, repair, or replace damaged cells. Makes 2 identical cells (same number of chromosomes as the original). Example: When you get a wound, mitosis helps create new skin cells to heal it.

41. Stages of Mitosis Prophase – The DNA coils into chromosomes. The nuclear membrane disappears. Metaphase – Chromosomes line up in the middle of the cell. Anaphase – Chromosomes are pulled apart to opposite sides. Telophase – New nuclear membranes form around the two sets of chromosomes. Cytokinesis – The cell splits into two identical daughter cells .

42. Meiosis Happens in sex cells (sperm for boys, egg for girls). Purpose: To create Gametes for reproduction. Makes 4 different cells each half the number of chromosomes. Example: When a baby is formed, it starts from a sperm and an egg made through meiosis.

43. Stages of Meiosis Meiosis I – Separates pairs of chromosomes: Prophase I – Chromosomes pair up and exchange genes ( crossing over ). Metaphase I – Pairs line up in the center. Anaphase I – Pairs are pulled apart (not the chromosomes yet!). Telophase I and Cytokinesis – Cell splits into 2 cells.

44. Stages of Meiosis Meiosis II – Like mitosis but with half the chromosomes: Prophase II – Chromosomes get ready again. Metaphase II – Chromosomes line up in the center. Anaphase II – Chromosomes are pulled apart. Telophase II and Cytokinesis – Both cells divide again → Total of 4 cells .

45. Feature Mitosis Meiosis Type of cells Body cells Sex cells # of cell divisions 1 2 Final cells 2 identical cells 4 non-identical cells Purpose Growth & repair Reproduction Chromosomes Same as original Half of the original

46. Cell- ebrate What You’ve Learned!