Mitosis: Making two identical cells from one. Why do cells need to divide?

Vocabulary Words Chromatin = DNA that is spread out and not visible with a light microscope Chromosome = one molecule of DNA that contains many genes. When it is tightly packed, it is visible with a light microscope. Gene = a section of the chromosome that contains the instruction to make a protein

Vocab Cont’d Sister chromatid = one of two copies of a chromosome that are attached to one another Mitosis = cell division in eukaryotes Centrioles = The structures in a dividing animal cell that organizes the spindle fibers Spindle fibers = The long protein molecules that attach centrioles to chromosomes and help move the chromosomes during cell division

Purpose of Mitosis -Growth - Cell replacement - Bacterial reproduction - Where is mitosis happening in you right now? Talk with a partner and come up with at least 3 places and why you think mitosis is happening there.

Mitosis What is the result of mitosis/cell division? If two new cells are made, what must happen in the cell before division?

DNA Replication Where is DNA located in the cell? Why must there be copies made? What would happen if there were no copies of DNA made?

DNA Replication Why do we need two exact copies of DNA for cell division to occur?

How many chromosomes are in the original cell? How many chromosomes are n the “daughter cells?”

Mitosis Happens in Stages which Scientists have Named

Interphase - Cell doing normal activities - DNA in nucleus replicates (makes a copy of itself) DNA REPLICATION – Making an exact copy of a chromosome

Prophase Nuclear membrane disappears DNA becomes visible as it “condenses” into chromosomes

Metaphase - Chromosomes line up along the center (middle) of the cell

Anaphase - One replicated chromosome moves to each side of the cell (chromatids pull apart)

Telophase and Cytokinesis An identical chromosome is now on either side of the cell Nuclear membrane begins to reform Begins to break apart into two new cells

Look at the diagram of onion root tip cells Look at the diagram of onion root tip cells. Write the stages of mitosis in order on your paper. Write the correct letter by the cell in that stage.

Cell Cycle What do cells do when they are not undergoing mitosis? What might a pancreas cell be doing? What might a plant leaf cell be doing?

Mitosis Lab Look at the onion root tip slide using a microscope Draw a 1x1in sketch of ONE cell in each stage (how many cells will you be drawing total?) Label the stage and describe what is happening during each stage Why would we use onion root tips to study mitosis?