Cell Division and Mitosis One parent cell giving rise to two identical daughter cells

What is Mitosis? Mitosis is the process of duplication of chromosomes and division of the nucleus prior to cell division.

5 Phases of Mitosis Interphase Prophase Metaphase Anaphase Telophase

Interphase Includes the time that the cell is not actively dividing so may last a long time The cell carries out its normal life functions during this phase DNA is in the form of chromatin – long threadlike strands, not visible with light microscope

Late Interphase Chromosomes have replicated. Nuclear membrane is still intact Nuclei stained blue; Center and right cell in interphase Public Domain: h_Hoechst_33258.jpg h_Hoechst_33258.jpg h_Hoechst_33258.jpg

Interphase = Chromatin

Prophase Chromatin coils into chromatids and become easily visible with light microscope. Duplicate chromosomes are attached at the centromeres. Fluorescence microscope image of two mouse cell nuclei in prophase (scale bar is 5 µm).

Prophase In the cell: Centrioles move to opposite ends of the cell (animal cells) Spindle forms Nucleolus disappears Nuclear membrane breaks down

Different Forms of Chromosomes (1) Chromatin during interphase with centromere. (2) Condensed chromatin during prophase. (Two copies of the DNA molecule are now present) (3) Sister chromatids from the end of prophase through anaphase. Image modified from

Prophase Chromosomal components: (1) Chromatid (2) Centromere (3) Short arm (4) Long arm

Metaphase The chromosomes have aligned along the equator of the cell attached to the spindle fibers by the centromeres Some rights reservedSome rights reserved by Carolina Biological Supply CompanyCarolina Biological Supply Company

Metaphase

Anaphase Each centromere splits allowing identical sister chromatids to separate and move along the spindle fibers toward opposite ends of the cell.

Anaphase Early Anaphase: The chromosomes are starting to migrate toward opposite poles. Late Anaphase: The contraction of the spindle fibers has moved the separate masses of chromatids farther from the equator. Some rights reservedSome rights reserved by Carolina Biological Supply CompanyCarolina Biological Supply Company Onion Root Tip Whitefish egg

Anaphase

Telophase The chromatids have reached the poles. The chromatids uncoil back into chromatin. Each set of chromosomes becomes incorporated in a new nucleus as the nuclear membrane reforms. Cytokinesis or cell division now occurs.

Daughter Cells in Interphase After cytokinesis: Cells may enter a prolonged period of interphase when all the processes that normally take place in the cell occur, except for cell division. Cells may repeat the steps of mitosis and divide again

Phases of Mitosis – Another Look Public Domain:

Mitosis in Onion Root Tip org/wiki/File:Onion_root_mi tosis.jpg org/wiki/File:Onion_root_mi tosis.jpg Can you find: ProphaseMetaphaseAnaphaseTelophase