- Slides: 27
CELL DIVISION & CANCER
Cell Division Vocabulary somatic cell – All cells in your body except your gametes; a cell whose genes will not be passed on to future generations. diploid (2 n) – a cell with 2 chromosome sets; all body (somatic) cells § 2 n=46 for a human sex or germ cell - a 2 n (diploid) cell that is destined to become a gamete (egg or sperm); a cell whose genes can be passed on to future generations. • haploid (n) – a cell with 1 chromosome set; all gametes (sperm, eggs) • n=23 for a human (sperm: male and egg: Female)
Cell Division 2 kinds of cell division: 1. Mitosis: division of the somatic cell’s nucleus (2 n creates 2 n, asexual reproduction, identical copy) Pancreatic cells 2. Meiosis: creation of new sex cells (2 n creates n, sexual reproduction, different from each other) Sperm cells Human egg cell
Cell Cycle A typical cell goes through a process of growth, development, and reproduction called the cell cycle. Any mutation affecting the cell cycle may cause cell to grow and divide without control (cancer) Click Image
Cell Cycle Interphase G 1 S G 2 M phase Mitosis Cytokinesis Prophase Metaphase Anaphase Telophase
Cell Cycle: Interphase The longest phase in the cell cycle is interphase. DNA is in chromatin form (relatively loose fiber composed of DNA wrapped around histone proteins) The 3 stages of interphase are called 1. G 1 (Gap 1) 2. S (Synthesis) 3. G 2 (Gap 2)
Interphase: G 1 -phase Cells spend most of their time in G 1 The cell grows and performs its normal function. Prepares for S phase Control of cell division occurs in G 1: a cell that isn’t destined to divide goes into G 0(resting phase, non-dividing phase). MUSCLE CELL NEURON G 0
Interphase: S-phase The S phase (“Synthesis”) is the time when the DNA is replicated or copied. Sister chromatids (the copies of the DNA strands) are attached to each other at the centromere. Parent strands Daughter strands
Interphase: S-phase DNA duplicates Centromere Remember the DNA is not condensed, it is still chromatin. The centromere is the place where the sister chromatids are attached to each other.
Interphase: G 2 -phase G 2 is the period between S and mitosis. DNA replication is checked and the cell is getting ready to divide.
G 2: More growth and preparation for mitosis
Mitotic (M) Phase: Cell Division During the M Phase, 1 parent cell divides into 2 daughter cells. (All living cells come from other living cells. ) The M phase is divided into 2 parts: During mitosis, the nucleus of the cell divides, forming two nuclei with identical genetic information. During cytokinesis, the cytoplasm divides and the cell splits in two.
M phase: Mitosis produces two genetically identical cells called daughter cells which are 2 n. Mitosis is comprised of the following stages: Prophase 2. Metaphase 3. Anaphase 4. Telophase 1.
M Phase: Mitosis - Prophase In prophase, the cell begins the process of division. The chromatin condenses. Chromatin coils up to form X shaped chromosomes. duplicated chromosome
Prophase (continued) Nuclear envelope disappears. Centrioles migrate to opposite poles of the cell. Spindle apparatus forms: spindle fibers (microtubules) grow out from centrioles.
Prophase: Check for Understanding Spindle fibers Aster Centriole Centromere Sister chromatids
M Phase: Mitosis - Metaphase The chromosomes line up at the equator of the cell (metaphase plate), The centrioles are at opposite poles The spindle fibers are attached to opposite sides of the centromeres. centromere Centriole Spindle fibers Metaphase plate Apparatus
Metaphase in picture
M Phase: Mitosis - Anaphase In anaphase, the centromeres divide because spindle fibers pull the sister chromatids in opposite direction. At this point, each chromosome goes from having 2 sister chromatids to being 2 separate chromosomes The spindle fibers contract and the chromosomes are pulled to opposite poles. Cell elongates Spindle fibers Centromere breaks
M Phase: Mitosis - Telophase Chromosomes arrive at opposite poles of the cell. The nuclear envelope re- forms around the two sets of chromosomes. Chromosomes uncoil and is now chromatin once again Spindle apparatus disassembles. Division of the Nucleus is now complete
M Phase: Cytokinesis is the division of the cytoplasm. Cytokinesis starts during telophase but IS NOT PART OF TELOPHASE (OR MITOSIS)
Cytokinesis in animal cells In animal cells, the cell membrane pinches in and forms a Cleavage Furrow that separates the Daughter Cells Cleavage furrow in a dividing frog cell.
Cytokinesis in Plant Cells In plant cells, a new cell wall forms at the Cell Plate and separates Daughter Cells. Cell Plate forming
ANIMAL VS. PLANT MITOSIS ANIMAL CELL Centriole present Daughter cells separated by cleavage furrow PLANT CELL No visible centriole Daughter cells separated by cell plate
What do living things use Mitosis for? Maintains Chromosome number in specie’s somatic cells (2 n – 2 n) Growth of a living thing Zygote to embryo to fetus to baby to adult Repair Heal wounds Replace worn out cells Skin, blood, etc Asexual Reproduction All offspring identical to parent (2 n) Limits variation
Proteins Control the Cell Cycle Proteins control the cell cycle A mutation in DNA that changes the shape of a protein may make the protein malfunction The cell cycle is When cells from a cancerous uncontrolled and may tumor get into the blood stream allow mitosis to go they can travel all over the body unchecked and occur very creating more tumors. rapidly. This can cause the formation of a tumor.