Unit 2 Lesson 1 Mitosis Copyright © Houghton Mifflin Harcourt Publishing Company

Splitsville! Why do cells divide? Unit 2 Lesson 1 Mitosis Splitsville! Why do cells divide? Cell division takes place for different reasons. Cell division is important for asexual reproduction, which involves only one parent organism. Most growth in a multicellular organism happens because cell division produces new cells. Cell division also produces cells for repair. Copyright © Houghton Mifflin Harcourt Publishing Company 2

What happens to genetic material during cell division? Unit 2 Lesson 1 Mitosis What happens to genetic material during cell division? The genetic material in cells is called DNA (deoxyribonucleic acid). In eukaryotic cells, DNA is found in the nucleus. A DNA molecule contains the information that determines the traits that a living thing inherits and needs to live. Copyright © Houghton Mifflin Harcourt Publishing Company 3

What happens to genetic material during cell division? Unit 2 Lesson 1 Mitosis What happens to genetic material during cell division? During most of a cell’s life cycle, DNA is found in a mass of loose strands called chromatin. Before cell division, DNA is duplicated. As cell division begins, the chromatin is compacted into visible structures called chromosomes. Copyright © Houghton Mifflin Harcourt Publishing Company 4

What happens to genetic material during cell division? Unit 2 Lesson 1 Mitosis What happens to genetic material during cell division? A duplicated chromosome is made of two identical structures called chromatids. Copyright © Houghton Mifflin Harcourt Publishing Company 5

Around and Around What are the stages of the cell cycle? Unit 2 Lesson 1 Mitosis Around and Around What are the stages of the cell cycle? The life cycle of a eukaryotic cell, called the cell cycle, can be divided into three stages: interphase, mitosis, and cytokinesis. Copyright © Houghton Mifflin Harcourt Publishing Company 6

What are the stages of the cell cycle? Unit 2 Lesson 1 Mitosis What are the stages of the cell cycle? Interphase is the stage in the cell cycle during which the cell is not dividing. The cell grows to about twice the size it was when it was first produced. It produces various organelles and engages in normal life activities. Changes that occur during interphase prepare a cell for division. Copyright © Houghton Mifflin Harcourt Publishing Company 7

What are the stages of the cell cycle? Unit 2 Lesson 1 Mitosis What are the stages of the cell cycle? In eukaryotic cells, mitosis is the part of the cell cycle during which the nucleus divides. Prokaryotes do not undergo mitosis because they do not have a nucleus. Mitosis results in two nuclei that are identical to the original nucleus. When mitosis is complete, the cell has two identical sets of chromosomes in two separate nuclei. Copyright © Houghton Mifflin Harcourt Publishing Company 8

What are the stages of the cell cycle? Unit 2 Lesson 1 Mitosis What are the stages of the cell cycle? Cytokinesis is the division of the parent cell’s cytoplasm. Cytokinesis starts during the last step of mitosis and eventually forms two complete cells. In cells that have a cell wall, a cell plate forms during cytokinesis. The cell plate separates the cell into two new cells. Copyright © Houghton Mifflin Harcourt Publishing Company 9

Phasing Out What are the phases of mitosis? Unit 2 Lesson 1 Mitosis Phasing Out What are the phases of mitosis? There are four phases of mitosis: prophase, metaphase, anaphase, and telophase. By the end of the four phases, the cell will have two identical nuclei. Copyright © Houghton Mifflin Harcourt Publishing Company 10

What are the phases of mitosis? Unit 2 Lesson 1 Mitosis What are the phases of mitosis? In prophase, the chromatin in the nucleus condenses into chromosomes. The membrane around the nucleus breaks down. Copyright © Houghton Mifflin Harcourt Publishing Company 11

What are the phases of mitosis? Unit 2 Lesson 1 Mitosis What are the phases of mitosis? In metaphase, the chromosomes line up in the middle of the cell. Copyright © Houghton Mifflin Harcourt Publishing Company 12

What are the phases of mitosis? Unit 2 Lesson 1 Mitosis What are the phases of mitosis? In anaphase, the chromatids of each chromosome are pulled to opposite sides of the cell. Copyright © Houghton Mifflin Harcourt Publishing Company 13

What are the phases of mitosis? Unit 2 Lesson 1 Mitosis What are the phases of mitosis? In telophase, a new nuclear membrane forms around each group of chromosomes, which become less condensed. Cytokinesis begins during this phase. Copyright © Houghton Mifflin Harcourt Publishing Company 14

What are the phases of mitosis? Unit 2 Lesson 1 Mitosis What are the phases of mitosis? After mitosis, cytokinesis results in two new cells, and the two new cells start the cell cycle again. Copyright © Houghton Mifflin Harcourt Publishing Company 15