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Sam’S PuPPy • Body cell reproduction involves producing new daughter cells for growth of tissues as well as repair and replacement of old cells. • Most living body cells eventually divide into two cells through a process called mitosis. This can happen because food and nutrients are broken down and become building blocks for new living materials like the new cells produced during cell division. LT #5 I can DESCRIBE how cells multiply. Why do cells divide? • Weeds can grow pretty fast. In fact, the stems and roots of a fastgrowing plant seem to get longer over night. Where do the new stem and root parts come from? – They are made when existing cells divide to form new cells. This process is called cell division. Why do cells divide? • Eventually cells need to duplicate. There are two types of cell division, mitosis (growth) and meiosis (reproduction). • Mitosis allows organisms to grow larger, and also helps organisms replace injured cells. GROWTH! Mitosis • The big idea to remember is that mitosis is the simple duplication of a cell and all of its parts. • It duplicates its DNA and the two new cells (daughter cells: cells resulting from the replication and division of a single parent cell) have the same pieces and genetic code. Two identical copies come from one original. Start with one; get two that are the same. Get the idea? Mitosis • Before a eukaryotic cell (a cell with an organized nucleus) divides, the genetic material in the nucleus of the cell copies itself. • When the cell divides, the nuclear material splits in half so that each daughter cell gets genetic material that is the same as that of the parent cell. Mitosis • The dividing of the nuclear material is known as mitosis. • In the last stage of cell division, the cytoplasm divides as well. • There are now two complete cells where there used to be one. Science Alert! • The terms mitosis and cell division are sometimes used interchangeably. • BUT…mitosis really refers only to the dividing of the nuclear material. • While…cell division is the complete process of copying and dividing the whole cell. Cell Division Phases • Beyond the idea that two identical cells are created, there are predictable stages or phases in the cell division process. • These steps ensure that the new daughter cells are the same as the cell from which they formed. Cell Division • There are 5 basic phases in the lifecycle of a cell. –Interphase –Prophase –Metaphase –Anaphase –Telophase Cell Division • The following mnemonic devices can help you remember the phases of cell division. • I prefer milk and tea. • I propose meeting at ten. • In Poland men are tall. • CAN YOU COME UP WITH YOUR OWN mnemonic device? Cell Division/Mitosis • Interphase – The stage before cell division starts. – As a cell prepares to divide, each chromosome in the nucleus makes an exact copy of itself. – Chromosomes: a structure made of DNA that contains the genetic info used to direct cell activity and make new cells Cell Division/Mitosis • Prophase – The nucleus prepares for cell division. – The genetic material shortens and thickens. – The chromosome copies are held together at their centers, so they form a sort of “X.” Cell Division/Mitosis • Metaphase – The two copies of each chromosome line up in the center of the cell. Cell Division/Mitosis • Anaphase – The copies separate. – One complete set of chromosomes is pulled to one side of the cell. – The other complete set is pulled to the other side of the cell. Cell Division • Telophase – Final stage of cell division – The cytoplasm pinches in at the center of the cell, dividing the cell in half. – When cell division is complete, two new daughter cells are formed. – The daughter cells are identical to the parent cell. Two identical copies come from one original. Start with one; get two that are the same. Get the idea? Mitosis Rap Time!