Cell Division The 100 trillion cells of your

Cell Division • The 100 trillion cells of your body are truly amazing, when you think that they all started from a single, fertilized egg. They stand as proof of the ability of human cells to reproduce grow ______ and __________.

• Reproduction generally means to make a copy ______ of something. Human reproduction, specifically, is a natural process where humans produce more humans. But, before we get too ahead of ourselves, we must start with the basics…

The Cell • The cell is the basic unit life. All living _________ organisms are made up of them. Some organisms are made up of a single cell, while others are made up of trillions of cells, like humans.

• Cells hold all of the equipment necessary to keep an organism alive. Cells must divide _________ to make new cells or the organism would die. There are two types of cells: Animal cells 1. ________ 2. ________ Plant cells Just like humans have organs to keep them alive, cells have __________ to organelles carry out all of their life processes.

Cell Division • As previously stated, human bodies contain trillions of cells. How did we go from a single cell to an entire person with skin, bones, and organs? Our cells had to divide over and over again.

Why do cells need to divide? • • Healing/repair Growth Replacing dead cells Reproduction

Cell Cycle pre-existing • All cells come from ___________ cells. Any new cell must come from another cell through the process of reproduction. Cells needed for repair, growth, or the maintenance of a species must use cell division.

• Cells live through a sequence of three steps called the cell cycle. The three stages are: 1. Interphase 2. Mitosis 3. Cytokinesis

1. Interphase • Before mitosis, during interphase, the cell identical set of its creates an ______ chromosomes. 46 92

1. Interphase • At the beginning of mitosis the chromosomes wind up into visible objects that can be seen with a light microscope. The chromosomes are now two chromatids joined at the ________ centromere Since the two chromatids are identical to each other, they are called _______ chromatids. sister

Chromosomes DNA • Chromosomes are made of _____. They carry all of the ______ information genetic used to help a cell grow, thrive, and reproduce. Segments of DNA in different patterns are genes called ____. Genes make you who you are.

• Mitosis happens in all types of dividing cells in the human body except with sperm and ova. 46 Human body cells contain ____ chromosomes (23 pairs). They are known as diploid (2 n), meaning they have two ______ sets of chromosomes, one from the ______ and one from the mother ________. father

2. Mitosis • There are four phases of mitosis. Each phase is used to describe what kind of change the cell is going through. The phases are prophase, metaphase, anaphase and telophase. P M A T

Prophase • The chromosomes in the nucleus condense. Pairs of centrioles move to opposite sides of the nucleus. Spindle fibers begin to form and bind to centrioles and centromeres.

Metaphase • The chromosomes line up in the middle of the cell. • *Remember M for “middle”.

Anaphase • The chromosomes are pulled apart by the spindle fibers. The sister chromatids are pulled to opposite sides of the cell. • *Remember A for “away”.

Telophase • There is now a complete set of chromosomes at each end of the cell. Spindle fibers begin to disappear. A nuclear membrane forms around each set of chromosomes. The cell starts to divide.

3. Cytokinesis • The cell splits into two identical cells called daughter cells. Each one contains 46 chromosomes, just like the parent cell.