Mitosis Cell Division

Agenda Chromosome Talk Cell Cycle Mitosis Overview

Mitosis Division of somatic cells (body) Daughter Cells Somatic Cell

Why Mitosis? Growth of the individual Repair and replace damaged tissue (as in healing of a cut) Reproduce asexually

Chromosomes First you duplicate DNA Why? You have 2 pairs of 23 chromosomes If cell splits, you will only have 1 pair Duplicate DNA, cell splits, still have 2 pair Sex chromosomes- X and Y: XX is female in humans, XY is male

Humans have 46 chromosomes 23 chromosomes from each parent. Most cells (somatic) have the normal number of chromosomes, they are are said to be diploid (i.e. skin cells). Some cells have half the number of chromosomes are said to be haploid (i.e. egg and sperm cells).

The chromosomes from the parents are of the same type, just different variations, so each child has 23 pairs of similar chromosomes. 22 pairs are known as autosomes that contain important genes. The last pair are known as the sex chromosomes (X and Y) and they have fewer genes and more of an influence on gender.

Chromatin in the cell during interphase is structurally loose

Stages of Cell Cycle Mitosis(M phase) –refers to the process of nuclear division Cytokinesis (C phase)- occurs after mitosis and is the actual physical division of the cell. Not included in mitosis Interphase: (G1, S, G2)

The Cell Cycle G1 Synthesis of DNA for Duplication of chromosomes Phase of rapid cell growth S Growth and preparation for cell division All cells come from preexisting cells Interphase: Cells grow, make structural proteins that repair damaged parts, transport nutrients, eliminate wastes, build proteins in preparation for mitosis Genetic information is called chromatin- all DNA in the nucleus (the tangled fibrous complex of the DNA and protein within a eukaryotic nucleus) Each chromosome duplicates itself. Each copy is attached together by a centromere. Forming Sister chromatids. Considered one chromosome. Most time is spent in interphase, nuclear division only a small portion G2 M

Interphase G1: primary growth phase. Increase in proteins and in the number of cell organelles. S: indicates the synthesis of DNA. a.k.a- DNA replication. G2: Chromosome condensation, preparation for mitosis; more growth.

Mitosis Inside the Cell Mitosis

Prophase Sister chromatids become visible Centrioles move to opposite sides of nucleus the spindle fibres begin to form nuclear membrane dissolves & disappears

Prophase Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Metaphase Sister chromatids fully attached to spindle fibres chromatids line up in the middle of the cell

Metaphase Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Anaphase Sister chromatids separate from their partners to become individual chromosomes pulled by spindle fibres to opposite poles of cell

Anaphase Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Telophase chromosomes begin to unwind take form of chromatin spindle fibres dissolve and nuclear membrane forms around the chromosomes

Telophase Q: What did one chromosome say to the other? A: It's telophase, man. UUUNNNNNWWWWWIIIINNNNNDDDD... Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Cytokinesis cell divides the cytoplasm and organelles into two portions cell membrane cleaves inward 2 identical daughter cells result

Cytokinesis One cell is undergoing mitosis and their neighbor looks over and says 'nice cleavage!' The first cell replies 'You should see my daughter cells!' Q: Why did the cell where such a tight dress? A: To improve its cleavage furrow.

Mitosis Summary Two divisions occur during cell division Nuclear division (mitosis) and cytoplasmic division (cytokinesis) During interphase genetic material is replicated During G1 there are 46 single stranded chromosomes and then after the S phase there are 46 double stranded chromosomes 2 Identical daughter cells produced Both daughter cells are diploid 2n=46 Embryonic growth is a result of repeated mitotic divisions A zygote is one cell after fertilization. As divisions occur, specialization occurs.

Any Questions?

References Edupic Graphical Resource: Cells http://www.edupic.net/cells.htm