BIO_SC 1010 1st Edition Lecture 9 Outline of Last Lecture I. Noncoding Regions of DNAII. Short Tandem RepeatsIII. DNA ProfilingOutline of Current Lecture I. What is a Somatic Cell?II. Cell DivisionIII. Stages of the Cell CycleIV. Cell Division is tightly regulatedV. What is Cancer?VI. Fighting CancerCurrent LectureWhat is a Somatic Cell?• Somatic Cells-Diploid: two copies of each chromosome; one from each parent-All normal cells are somatic: examples are liver, kidney, skin• Gametic Cells-Haploid: one copy of each chromosome; half of the DNA-Sex cells are gametic: examples are sperm or eggsCell Division• The process by which a cell reproduces itself• Why do normal, healthy cells divide?-Cells divide for growth and development-Cells divide for cell replacement -Cells divide to heal woundsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.• How do cells divide?-A cell doesn’t simply slit in half to form two new cells. If it did, each new cell would be smaller than the original cell, and each cell would lose half of its contents with each division.-Before a cell divides, it copies its contents so that each new cell has the same amount of organelles, DNA, and cytoplasm as the original cell.• Through cell division, one parent cell divides into two new daughter cells, each of which is identical to the parent cell• The purpose of the cell cycle is to replicate cells• The cell cycle is an ordered sequence of stages through which a cell progresses in order to divide during its lifeStages of the Cell Cycle• The cell cycle consists of preparatory phases (collectively known as interphase) and division phases (mitosis and cytokinesis)• The cell cycle consists of preparatory phases (collective known as interphase and divisionphase (mitosis and cytokinesis) • Interphase-the stage of the cell cycle in which cells spend most of their time, preparing for cell division-is divided into three stages: G1, S, and G2-during G1: cells grow and prepares to divide; both DNA and organelles-during S: chromosomes are duplicated; DNA replication occurs-a sister chromatid is ones of the two identical DNA molecules-they make a duplicated chromosome following DNA replication-the sister chromatids are joined together at the centromere -during G2: the cell prepares for division• During mitosis, the sister chromatids of each chromosome are separated from one another-setting up the two identical nuclei of the daughter cells• Phases of Mitosis1. Interphase (before mitosis)-the chromosomes are loosely gathered in the nucleus-chromosomes replicate into two sister chromatids 2. Prophase -replicated chromosomes begin to coil up-nuclear membrane begins to disassemble-protein fibers of the mitotic spindle begins to form 3. Metaphase-spindle fibers from opposite ends of the cell pull on chromosomes-chromosomes align along the middle of the cell4. Anaphase-spindle fibers shorten ad pull sister chromatids to the opposite ends of the cell5. Telephase-identical set of chromosomes reaches each pole-spindle fibers dissemble-nuclear membrane forms around each set of chromosomes to form the daughter cell nuclei6. Cytokinesis (after mitosis) -cytoplasm divides into two cells, each containing a full complement of organelles and DNA-cell membrane pinches in to completely surround each new daughter cell • The cell cycle starts over with two newly formed identical daughter cells in interphase-each daughter cell has the same number of chromosomes as the parent cell• Cytokinesis in animal cells:-the parent animal cell is pinched into two, leaving two independent offspring cells• Cytokinesis in plant cells:-plant cells divide their cytoplasm by forming a cell plate along the center line of the cellCell Division is tightly regulated• Cell Cycle checkpoints -ensure that each stage of the cell cycle in completed -preventing a cell from progressing to the next stage until it accurately finishes the current stage• Apoptosis-when a normal cell has irreparable damage-programmed cell death to prevent cells from producing more damaged daughter cellsWhat is Cancer?• Cancer is a disease of unregulated cell division-cells divide inappropriately and accumulate, in some instances forming a tumor -cancer cells have damaged checkpoint mechanisms, allowing them to divide when they should not-the damaged cells also bypass apoptosis, passing the damaged DNA to each daughter cellFighting Cancer• Surgery to remove the cancerous tumor is effective for certain solid tumors-not an effective treatment for blood cancers or cancers that have undergone metastasis• Metastasis: the spread of cancer cells from one location in the body to another • Chemotherapy uses drugs to interfere with cell division to treat cancer• Radiation therapy has high-energy radiation beams are used to kill dividing cells, severely damaging molecules ad DNA to trigger apoptosis • Side-effects -side effects of chemotherapy and radiation therapy can be quite severe-herbal supplements may complement cancer treatment by reducing the severity of traditional side effects and enhancing the effect of