Cell Division: Mitosis & Meiosis How cells pass on DNA to their offspring

Why do cells divide?

Cell Theory A fundamental understanding in biology is the cell theory. It says that All living things are composed of cells Cells are the smallest unit of life All cells come from preexisting cells by cell division In order for an organism to grow or reproduce, its cells have to make new cells – they have to divide.

Preparation for Cell Division When a cell divides, it passes on its DNA – the molecules that contain its genetic material – to its offspring. Before a cell divides, it duplicates all its chromosomes (its DNA). That way it will be able to give one set of chromosomes to each of the cells it splits into. For this reason, cells that are about to divide have twice as much DNA as a normal cell.

Cell Division There are two types of cell division in human cells: Mitosis Meiosis We’ll look at each of these.

Mitosis Most of the cells in your body perform mitosis when they divide. In mitosis, the cell’s DNA is equally distributed to either side of the cell, and then the cell splits down the middle. This results in two daughter cells that have identical DNA to the original parent cell.

Meiosis Meiosis is the process by which organisms make gametes (eggs or sperm). In meiosis, the parent cell goes through two divisions of its chromosomes and splits itself in half twice At the end of meiosis, four cells are formed that each have half the amount of DNA from the original cell

Meiosis, continued Because the cells that result from meiosis are either sperm or eggs, they need to have half the amount of DNA. A sperm will unite with an egg during sexual reproduction to form a new offspring Each of them will supply the new offspring with half its DNA

Mitosis & Meiosis Animations Explore the processes of Mitosis and Meiosis by following the link from Edmodo to the Mitosis & Meiosis Animations at cellsalive.com Create a table to compare & contrast the processes of mitosis and meiosis You don’t need to get all the small details, just the big idea of: Where the chromosomes go in general in the steps How many daughter cells are produced at the end Characteristics of the cells that are produced Purpose of the process overall

Ticket out of class Please put your name on your paper.

Ticket out of class What does the cell theory say? What is the result of mitosis? What is the result of meiosis? What is one characteristic of prophase? What is one characteristic of metaphase? What is one characteristic of anaphase?