THE CELL CYCLE Mitosis Cellular Reproduction/Division

THE CELL CYCLE 1. The regular sequence of growth and division that cells undergo is known as the cell cycle. 1. The regular sequence of growth and division that cells undergo is known as the cell cycle. 2. The cell cycle is divided into 3 main stages. 2. The cell cycle is divided into 3 main stages.

STAGE 1 – INTERPHASE 3. When you look at cells under a microscope, you mostly see them in a non-reproducing state. 3. When you look at cells under a microscope, you mostly see them in a non-reproducing state. 4. The non-reproducing stage is called interphase. 4. The non-reproducing stage is called interphase. 5. Interphase is the first stage of the cell cycle. 5. Interphase is the first stage of the cell cycle.

STAGE 1 – INTERPHASE 6. Interphase is the period before cell division occurs. 6. Interphase is the period before cell division occurs. 7. During interphase, the cell is using energy to carry out the basic cell functions. 7. During interphase, the cell is using energy to carry out the basic cell functions. 8. At the same time, new cell parts such as ribosomes and mitochondria are being produced. 8. At the same time, new cell parts such as ribosomes and mitochondria are being produced.

INTERPHASE – GROWTH 9. During the first part of interphase, the cell doubles in size and produces all the structures needed to carry out its functions. 9. During the first part of interphase, the cell doubles in size and produces all the structures needed to carry out its functions. 10. The cell enlarges its endoplasmic reticulum, makes new ribosomes, and produces enzymes. 10. The cell enlarges its endoplasmic reticulum, makes new ribosomes, and produces enzymes.

INTERPHASE – GROWTH 11. The mitochondria makes copies of itself during the growth phase also. 11. The mitochondria makes copies of itself during the growth phase also. 12. During this time the cell will grow and reach its full size and structure. 12. During this time the cell will grow and reach its full size and structure.

INTERPHASE – DNA REPLICATION 13. Once a cell has reached its mature size, the next part of interphase begins. 13. Once a cell has reached its mature size, the next part of interphase begins. 14. When the cell makes a copy of the DNA in its nucleus it is called replication. 14. When the cell makes a copy of the DNA in its nucleus it is called replication.

INTERPHASE – DNA REPLICATION 15. DNA is found in the chromatin inside the cell’s nucleus. 15. DNA is found in the chromatin inside the cell’s nucleus. 16. DNA holds all the information that the cell needs to carry out its functions. 16. DNA holds all the information that the cell needs to carry out its functions.

INTERPHASE – DNA REPLICATION 17. DNA replication is very important, because each new cell that is produced must have a complete set of DNA in order to survive. 17. DNA replication is very important, because each new cell that is produced must have a complete set of DNA in order to survive. 18. At the end of DNA replication, the cell contains two identical sets of DNA. 18. At the end of DNA replication, the cell contains two identical sets of DNA. 19. Once the DNA has been replicated, the cell will prepare to divide. 19. Once the DNA has been replicated, the cell will prepare to divide.

STAGE 2 – MITOSIS 20. Mitosis is the stage during which the cell’s nucleus divides into two new nuclei. 20. Mitosis is the stage during which the cell’s nucleus divides into two new nuclei. 21. During mitosis, one copy of the DNA is distributed into each of the two daughter cells. 21. During mitosis, one copy of the DNA is distributed into each of the two daughter cells. 22. Mitosis is divided into 4 parts or phases: prophase, metaphase, anaphase, and telophase (cytokinesis). 22. Mitosis is divided into 4 parts or phases: prophase, metaphase, anaphase, and telophase (cytokinesis).

MITOSIS – PROPHASE 23. During prophase, the nuclear membrane begins to break down, and the chromatin inside the nucleus is growing thicker and shorter. 23. During prophase, the nuclear membrane begins to break down, and the chromatin inside the nucleus is growing thicker and shorter. 24. The chromatin condenses and coils, like fishing line wrapping around a ball. 24. The chromatin condenses and coils, like fishing line wrapping around a ball. 25. The condensed chromatin begins to look like tiny rods. 25. The condensed chromatin begins to look like tiny rods. 26. Since the cell’s DNA has replicated each rod of chromatin has doubled. 26. Since the cell’s DNA has replicated each rod of chromatin has doubled.

MITOSIS – PROPHASE 27. Each of these rods of chromatin is an exact copy of the other. 27. Each of these rods of chromatin is an exact copy of the other. 28. These doubled rods of chromatin are now called chromosomes. 28. These doubled rods of chromatin are now called chromosomes. 29. Each individual strand or rod making up the chromosome is called a chromatid. 29. Each individual strand or rod making up the chromosome is called a chromatid. 30. The structure holding the chromatids together is called a centromere. 30. The structure holding the chromatids together is called a centromere.

MITOSIS – PROPHASE 31. By this time the nucleus has completely disappeared. 31. By this time the nucleus has completely disappeared. 32. At the same time the 2 pairs of centrioles found in each cell begin to separate and go to opposite ends or poles of the cell. 32. At the same time the 2 pairs of centrioles found in each cell begin to separate and go to opposite ends or poles of the cell. 33. A structure called a microtubule then forms between the pairs of centrioles. 33. A structure called a microtubule then forms between the pairs of centrioles.

MITOSIS - METAPHASE 34. As metaphase begins the chromosomes are scattered around the area that was once the nucleus. 34. As metaphase begins the chromosomes are scattered around the area that was once the nucleus. 35. The chromosomes then begin to line up along the middle of cell known as the equator. 35. The chromosomes then begin to line up along the middle of cell known as the equator. 36. During metaphase the microtubles connecting the centrioles begin to get longer. 36. During metaphase the microtubles connecting the centrioles begin to get longer.

MITOSIS – ANAPHASE 37. At the beginning of anaphase the centromeres split. 37. At the beginning of anaphase the centromeres split. 38. The two chromatids that were once joined by the centromere begin to separate and move apart. 38. The two chromatids that were once joined by the centromere begin to separate and move apart. 39. The two chromatids that were once joined are known as sister chromatids. 39. The two chromatids that were once joined are known as sister chromatids.

MITOSIS – ANAPHASE 40. After separating, the sister chromatids are pulled to the opposite poles. 40. After separating, the sister chromatids are pulled to the opposite poles. 41. At the end of anaphase, there is one set of single-stranded chromosomes at each end of the cell. 41. At the end of anaphase, there is one set of single-stranded chromosomes at each end of the cell.

MITOSIS – TELOPHASE 42. Telophase is the final phase of mitosis, when the cell begins to divide in two. 42. Telophase is the final phase of mitosis, when the cell begins to divide in two. 43. The cell membrane begins to pinch together at the center. 43. The cell membrane begins to pinch together at the center. 44. This process is called cytokinesis. 44. This process is called cytokinesis.

MITOSIS – TELOPHASE 45. During cytokinesis, the cytoplasm divides and the organelles are divided into the two sides of the cell. 45. During cytokinesis, the cytoplasm divides and the organelles are divided into the two sides of the cell. 46. As the cell pinches in half, a nuclear membrane forms from the endoplasmic reticulum on each end of the cell and encloses each set of chromosomes. 46. As the cell pinches in half, a nuclear membrane forms from the endoplasmic reticulum on each end of the cell and encloses each set of chromosomes.

MITOSIS – TELOPHASE 47. The chromosomes then join together as one mass of chromatin. 47. The chromosomes then join together as one mass of chromatin. 48. At the conclusion of cytokinesis, the cell membrane completely separates and forms two identical cells. 48. At the conclusion of cytokinesis, the cell membrane completely separates and forms two identical cells. 49. These identical cells are called daughter cells. 49. These identical cells are called daughter cells.

LENGTH OF THE CELL CYCLE 50. The length of the cell cycle is different for each different type of cell. 50. The length of the cell cycle is different for each different type of cell. 51. The length of each phase of the cell cycle is also determined by the type of cell. 51. The length of each phase of the cell cycle is also determined by the type of cell. 52. Some cells, such as those in bone marrow that form red blood cells, reproduce rapidly. 52. Some cells, such as those in bone marrow that form red blood cells, reproduce rapidly.

LENGTH OF THE CELL CYCLE 53. The cell cycle for red blood cells lasts less than 1 hour. 53. The cell cycle for red blood cells lasts less than 1 hour. 54. Human liver cells divide only when new cells are needed to help repair a wound. 54. Human liver cells divide only when new cells are needed to help repair a wound. 55. Some cells, such as brain cells, never divide but remain in interphase their whole life. 55. Some cells, such as brain cells, never divide but remain in interphase their whole life.

LENGTH OF THE CELL CYCLE 56. It is estimated that 25 million cell divisions occur every second in the adult human body. 56. It is estimated that 25 million cell divisions occur every second in the adult human body.