Unit 2 Lesson 1 Mitosis Copyright Houghton Mifflin

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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