IB Biology: Cell Division

IB Biology: Cell Division Cell Division Outline the stages in the cell cycle, including interphase (G1, S, G2), mitosis, and cytokinesis Stages of the Cell Cycle: ❖ Interphase ➢ G1 (Gap 1) ➢ S phase ➢ G2 (Gap 2) ❖ Mitosis ❖ Cytokinesis *Note: this is a cell cycle. There is no first or last Eukaryotic cells reproduce using cell division and their life can be thought of as a series of events called the cell cycle. The M phase consists of mitosis and cytokinesis. This phase only takes up a small percentage of the cell cycle. ❖ Mitosis is when a cell divides its nucleus into two identical nuclei. It is not the same thing as cell division as only the nucleus divides; not the whole cell. ❖ Cytokinesis follows shortly after. It is the division of the cytoplasm, resulting into two identical daughter cells, each with their own nucleus. The Interphase consists of G1, S, and G2. It is the longest phase. During interphase, DNA molecules are uncoiled so the genes on them can be transcribed, a process allowing protein synthesis. ❖ Gap 1 is when a cell grows, synthesizes proteins, and increases the number of mitochondria and chloroplast. ❖ S phase is when the chromosomes in the nucleus replicate in the nucleus resulting in two identical chromotids. ❖ Gap 2 is when the chromosomes in the nucleus condense, preparing for division. Some cells do not divide and indefinitely stay in G1. Such cells include: ❖ nerve cells ❖ brain cells State that tumours (cancers) are the result of uncontrolled cell division and that these can occur in any organ or tissue Tumors are the result of uncontrolled cell division. These can occur in any organ or tissue. When normal mitosis fails, due to a change in genes, the two daughter cells that the faulty cell creates will inherit those genes. The two daughter cells that the two faulty cells will each divide into will then also have the change in genes, creating four, abnormal cells. If those cells continue to reproduce, they will create a mass of cells called a tumor. These cells, as they are faulty, will not be able to able to carry out their specialized function, but will still take up the body’s energy and supplies. This tumor can spread to other parts of the body and become very large. The disease causes by tumors is called cancer. State that interphase is an active period in the life of a cell when many metabolic reactions occur, including protein synthesis, DNA replication adn an increase in the number of mitochondria and/or chloroplasts Interphase is an active period in the life of a cell when many metabolic reactions occur, including protein synthesis, DNA replication adn an increase in the number of mitochondria and/or chloroplasts Describe the events that occur in the four phases of mitosis (prophase, metaphase, anaphase and telophase) Explain how mitosis produces two genetically identical nuclei Phases of Mitosis: (an acronym to remember this is PMAT) Prophase ❖ chromosomes shorten and become fatter by supercoiling ❖ spindle microtubules grow from the poles and attach to centromeres ❖ in late prophase, the nuclear membrane begins breaking down Metaphase ❖ chromosomes move to the equator ❖ spindle microtubules attatch to the centromere of each sister chromatid ❖ nuclear membrane has completely broken down Anaphase ● spindle microtubules pull on the chromosomes, separating them to opposite poles of the cell Telophase ● chromosomes reach the poles ● nuclear membranes form around them ● the chromosomes uncoil *Note: this is a continuous process State that growth, embryonic development, tissue repair and asexual reproduction involve mitosis Mitosis is used in Eukaryotes to produce genetically identical cells. Such instances include: ❖ growth ❖ embryonic development ❖ tissue repair ❖ asexual reproduction