Cell Division

Outline Cells Review What is cell division? The Cell Cycle Interphase Mitosis 4 Steps of Mitosis Results of Mitosis Meiosis 8 Steps of Meiosis Results of Meiosis 2 Types of Cell Division

Cells Review Cell: smallest part of any living thing that carries out the functions necessary to support life Unicellular organism: living thing made up of 1 cell Multicellular organism: living thing made up of many cells

What is cell division? Cell division: a way to produce more cells –U–Usually 1 cell divides to make 2 cells Why is cell division important to multicellular organisms? –I–Its how they grow –R–Replace cells that have died Why is cell division important to unicellular organisms? –I–Its how they reproduce Cancer cell dividing E. Coli cell dividing

The Cell Cycle Cell cycle: everything that happens from 1 cell division to the next –2 parts 1. Interphase 2. Mitosis

Interphase Interphase: longest part of the cell cycle –The cell prepares to divide It grows in size It copies its DNA

Mitosis Mitosis: Part of the cell cycle when the cell actually divides to form 2 identical cells –Produces normal body cells Skin and muscle cells –The cells produced are identical to each other and to the original cell

Mitosis Mitosis has 4 steps: 1) Prophase 2) Metaphase 3) Anaphase 4) Telophase

4 Steps of Mitosis 1.Prophase –1–1 st step –N–Nucleus disappears –C–Chromosomes form in nucleus (look like X’s) These are how the DNA is stored in our cells Humans have 46 single chromosomes (23 pairs)

4 Steps of Mitosis 2.Metaphase –2 nd step –Chromosomes are lined up in the middle of the cell

4 Steps of Mitosis 3.Anaphase –3 rd step –Chromosomes are pulled apart –½ of each chromosome goes to each end of the cell

4 Steps of Mitosis 4.Telophase –4 th step –Cytoplasm begins to pinch in at center of cell –Eventually the 1 cell splits to form 2 cells Each new cell has its own nucleus and set of DNA

Results of Mitosis Mitosis produces normal cells in the body –Skin and muscle cells 1 cell splits to form 2 cells –The new cells are identical to each other –The new cells are also identical to the original cell

Meiosis Meiosis: cell division that produces reproductive cells –Reproductive cells are also called gametes –2 basic types of gametes (reproductive cells) Females – egg cells Males – sperm cells

Why Meiosis is Needed Fertilization: combining of sperm and egg cells to form a zygote –the zygote then grows and develops into a new organism –how living things reproduce sexually (combining of 2 cells)

Meiosis Meiosis has 8 steps –Basically goes through mitosis twice –There are 2 cell divisions

Meiosis 8 Steps of Meiosis: –Prophase 1 –Metaphase 1 –Anaphase 1 –Telophase 1 –Prophase 2 –Metaphase 2 –Anaphase 2 –Telophase 2

Results of Meiosis Meiosis produces reproductive cells (gametes) –Sperm and egg cells 1 cell splits to form 4 cells –The 4 new cells have ½ of the DNA that the original cell had –Haploid cells: cells with ½ of the amount of DNA of a normal cell –Diploid cells: cells with the normal amount of DNA

2 Types of Cell Division in Humans ½ the DNA Comparison to original cell Identical 23 (single) # of chromosomes in cells 46 (single) 4 # of cells produced 2 PMAT (1 and 2) Step names PMAT 8 # of steps 4 Reproductive cells Types of cells produced Normal body cells MeiosisCharacteristicsMitosis

2 Types of Cell Division in Humans