Mitosis Cell division

Agenda Cell cycle Mitosis Overview When things go wrong

The Basics: Genetic Material Chromatin in the cell during interphase is structurally loose

DNA Chromosome: DNA and associated proteins (nucleosomes/histones) that help condense chromosome into a smaller area during mitosis.

Chromosomes one chromosome (unduplicated) one chromosome (duplicated) Centromere Sister Chromatids Chromosome: a long piece of coiled DNA and proteins. The number of chromosome in each organism differs. 46 in humans. Seen only when the cell divides. Sister chromatids: 2 identical copies of the same chromosome Chromosome: a long piece of coiled DNA and proteins. The number of chromosome in each organism differs. 46 in humans. Seen only when the cell divides. Sister chromatids: 2 identical copies of the same chromosome

Cell theory All living things are made of cells Cells are the basic unit of life All cells come from pre-existing cells – Cell division is how life is perpetuated – Humans start out a s a single cell All living things are made of cells Cells are the basic unit of life All cells come from pre-existing cells – Cell division is how life is perpetuated – Humans start out a s a single cell

Why Divide? It is because the Surface area of a cell to its cytoplasm volume ratio affects the exchange of materials and wastes through the cell.

Why do cells divide? 1.If cells got too large, they would not be able to carry out their functions to survive 2.Growth: allow organisms to grow from a single cell to a multi-celled organism 3.Maintenance: allows new cells to replace worn-out or dead cells 4.Repair: regenerates damaged tissues

The Cell Cycle… Cells have a life cycle, called the cell cycle The sequence of events from one division to the next. Cell division is a very small part of a cells life. The cell cycle consists of 3 stages: – Interphase (growth and replication) – Mitosis (Nuclear(DNA) division) – Cytokinesis (cytoplasm division) Cells have a life cycle, called the cell cycle The sequence of events from one division to the next. Cell division is a very small part of a cells life. The cell cycle consists of 3 stages: – Interphase (growth and replication) – Mitosis (Nuclear(DNA) division) – Cytokinesis (cytoplasm division)

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) 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 Phase of rapid cell growth Synthesis of DNA for Duplication of chromosomes Growth and preparation for cell division G1G1 S G2G2 M

Interphase Most of the time of a cell’s life The stage between mitotic divisions Made of G1, S and G2 phase The cell grows takes in nutrients and produce proteins which are used for energy, growth and repair After a period of rapid growth (G1), the cell prepares for division by duplicating its chromosomes within the nucleus (S phase) After duplication there is another growth period. The cell ensures there is enough of everything for the division.

Interphase 1. Stage G1: primary growth phase. Increase in proteins and in the number of cell organelles. 2. Stage S: indicates the synthesis of DNA. A.k.a- DNA replication 3. Stage G2: Chromosome condensation, preparation for mitosis. Longest stage of cell cycle (The part where it does not divide). (G1, S, G2). Human cells contain 46 chromosomes during the G1 stage of interphase. 1. Stage G1: primary growth phase. Increase in proteins and in the number of cell organelles. 2. Stage S: indicates the synthesis of DNA. A.k.a- DNA replication 3. Stage G2: Chromosome condensation, preparation for mitosis. Longest stage of cell cycle (The part where it does not divide). (G1, S, G2). Human cells contain 46 chromosomes during the G1 stage of interphase.

The Expectations Describe the events that occur in the four phases of mitosis -PMAT-

Prophase * Sister chromatids present * Centrioles move to poles * During late prophase the nuclear envelope breaks down and each chromosome is connected to a spindle fibre by its centromere *chromatin condenses into chromosomes that contains 2 sister chromatids attached by a centromere *the nuclear envelope and nucleolus disintegrate *Mitotic spindle forms from microtubules *the pair of sister chromatids attach to the spindle at their centromeres. *in animal cells, a pair of centrioles move to each end, called the poles

Metaphase *Each chromosome becomes completely condensed. The chromosomes line up at the centre of the cell. Line up at the equitorial plate (equator) *The mitotic spindle (made of tubes) is complete and extend from each pole (centrioles) to the middle of the cell.

Anaphase The sister chromatids separate at the centromere. Each is now called a chromosome. The separated chromosome are pulled to opposite poles by the spindle fibres

Telophase Chromosomes have arrived at the poles Spindle disappears Centrioles replicate (in animals) Nuclear membrane reappears Nucleolus beocmes visible Chromosomes become chromatin

Cytokinesis The cell divides the cytoplasm and organelles into two portions (splitting known as cytokinesis) The cell membrane cleaves inward and in plant cells a cell plate forms, nuclear membrane reforms and spindle disappears 2 identical daughter cells result

Mitosis is an Animal cell Interphase Early Prophase Late Prophase Metaphase Anaphase Telophase Interphase The chromosomes condense, becoming shorter and thicker. The centrioles move to opposite poles of the cell and spindle fibres start to form. Chromosomes continue to condense. The centrioles assemble and spindle fibres attach to the centromeres of the chromosomes. The nuclear membrane starts to dissolve. Chromosomes line up at the equatorial plate. The nuclear membrane completely dissolves. The centromeres divide and the resulting chromosomes, move to opposite poles of the cell. An identical set (homologues) of chromosomes moves to each pole. Telophase Chromosomes lengthen again, the spindle fibres dissolve, and a nuclear membrane forms around the chromosomes. In humans, each new nucleus contains 46 unique chromosomes DNA replicated and cell prepares for division. In humans, 46 chromosomes are duplicated (46 pairs). w_g

Difference between Plant and Animal Cell Division Uses of Mitosis in Eukaryotic Cells: a. during growth of the individual. b. when tissues have been damaged and need to be repaired (as in healing of a cut). c. to reproduce asexually.

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 producedBoth daughter cells are diploid 2n=46Embryonic growth is a result of repeated mitotic divisions A zygote is one cell after fertilization. As divisions occur, specialization occurs.

Cell Death Apoptosis: regulated or controlled cell death of cells that are no longer useful. This is also used to control cells that have stopped performing properly – E.g your body must produces cells to fight a viral infection. When the infection is gone the cells are removed by apoptosis

Cancer Cancer: Disorder in which some of the body's cells lose the ability to control their growth. Tumour - repeated, uncontrolled cell division to form a mass of cells. This can happen in any organ. Some tumours grow large and spread to other parts of the body (metastasis). The diseases caused by the growth of tumours is known as cancer. – Tumours can be benign (harmless) or malignant (spread)

Causes Carcinogens (increase chances of mutation leading to cancer) – Radiation (gamma, UV, x-ray etc.) – Chemicals (textile dyes, paints and inks) – Viruses (hepititis B and C and HPV)

Removal Surgical- – physically excise the tumour cells Radiation- – using strong ionising or nuclear radiation beam which can be directed to a point and burn the cells Chemotherapy- – Uses chemicals to destroy all rapidly dividing cells by medication. Can destroy other rapidly dividing cells (hair, stomach/intestinal cells, sperm)

Cancer vs. Normal cells Cancer cellsNormal Cells Make exact copies of themselves during mitosis Do not stop reproducingReproduce cells Behave independentlyWork dependently/stick together Metstacize, no controlled death Self destruct “apoptosis” when old

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