Planet Earth and Its Environment A 5000-million year Journey

Part of the Patterns in Nature ModuleBiology in Focus, Preliminary CourseGlenda Childrawi and Stephanie HollisPatterns in NatureTopic 17: MitosisDOT Point(s)Identify mitosis as a process of nuclear division and explain its roleExplain the need for cytokinesis in cell divisionIdentify that nuclei, mitochondria and chloroplasts contain DNAbridlepath.wordpress.comThe Role of Mitosisjameskimlcop.blogspot.comIn multicellular organisms, cell division is a process that leads to the formation of new cells that form part of the organism and, as a result, contribute to the growth and repair of damaged tissue.

The Role of Mitosisnhptv.orgThe role of mitosis in multicellular organisms can be summarised as follows:Growth Repair of damaged tissue and replacement of worn out cellsGenetic stability: mitosis ensures the precise and equal distribution of chromosomes to each daughter nucleus, so that all resulting cells contain the same number and kind of chromosomes as each other and as the original parent.Asexual reproduction: growing plants from cuttingsThe Process of Mitosismeiosis-and-mitosis.pbworks.comMitosis is a highly co-ordinated process ensuring that the replicated chromosomes separate and are equally distributed to the daughter cells. Scientists have identified several distinct stages in the process. Well look at these now.

DNA replicates and become double strandedStep 1 Interphase:kvhs.nbed.nb.ca

The DNA coils up and the double stranded chromosomes become visible. The membrane surrounding the nucleus begins to break down.Step 2 Prophase:kvhs.nbed.nb.ca

The Chromosomes line up across the equator (middle) of the cell and a network of fibres appear, extending from the poles of the cell to each chromosome.Step 3 Metaphase:kvhs.nbed.nb.ca

The chromatids separate to become two independent chromosomes. The network of fibres contracts, pulling the chromosomes in opposite directions.

Step 4 Anaphase:kvhs.nbed.nb.ca

A nuclear membrane encloses the chromosomes and two nuclei form, each with the diploid number of chromosomes.Step 5 Telophase:kvhs.nbed.nb.ca

The cytoplasm divides and the result is two identical daughter cells. These cells grow in size in preparation for the next round of cell division.Step 6 Cytokinesis:kvhs.nbed.nb.caMitosiscelldynamics.orgThe outcome at the end of mitosis and cytokinesis is two daughter cells that have the identical chromosomes to each other and to the original parent cell.

Mitosismicro.magnet.fsu.eduWhen the cytoplasm divides, the organelles such as mitochondria and chloroplasts are distributed to the daughter cells in approximately equal numbers.

Mitosisen.wikipedia.orgIt is then necessary for the organelles in the cytoplasm to replicate so that they are not reduced in quantity. Mitochondria and chloroplasts contain their own small amounts of DNA and so they are able to replicate themselves.

Mitosishistoryoftheuniverse.comBy the time the daughter cells have grown to the size of the original parent cell, they have a similar number or organelles as the original cell had.

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