Transcript Chromosomes
Modern Biology Chapter 8: Cell Reproduction 8-1: Chromosomes • Chromosome structure – DNA coiled very tightly around proteins called histones 3 4 chromosome Sister chromatids Centromere 8 Numbers of chromosomes… Organism Ant Mosquito Drosophila melanogaster (fruit fly) Human Chimpanzee # of chromosomes 2 6 8, with 6 autosomal, and 2 sexual 46, with 44 autosomal and 2 sexual 48 Organism # of chromosomes Ichthyomys pittieri (semiaquatic rodent) 94 [highest for a mammal] Ophioglossum reticulatum (fern) 1200 or 1260 [highest plant] Aulacantha (protozoa) 1600 [highest] C:\Projects\Holt-RinehartWinston\HRWScience\HRWScience\Modern_Biology\Ch08\60121.ht ml Chromosome numbers • humans have 46 individual chromosomes in 23 pairs • homologous pairs: each member of a pair codes for the same trait, but may code for different values of the trait – both will code for eye color – one may carry code for green, the other blue Human Chromosome numbers • of the 46 chromosomes, –44 are autosomes • autosome: non-sex chromosome –2 are sex chromosomes • sex chromosome: chromosomes that determine the sex of an individual Human sex determination • XX- female • XY- male Female Parent Male Parent X Y X XX XY X XX XY Chromosome Number and Cell Type • diploid cells – diploid: cell that contain homologous pairs – most cells in human body – get one set from mom and the other from dad – 2n Chromosome Number and Cell Type • haploid cells – cell containing only one of each pair of homologous chromosomes – half the number of chromosomes –n – a.k.a.: gametes • Sperm and eggs Diploid v. Haploid Haploid Diploid chromosomes exist in pairs Chromosomes don’t exist in pairs Gametes The making of an individual n (egg) + n (sperm) 2n (individual with full set) Cell Division For autosomal cells Cell division in prokaryotes • binary fission: division of prokaryotic cell into two new cells • produces genetically identical individuals Binary Fission Cell division in eukaryotes • the cell cycle: repeating series of events in which new cells are made • Has three main functions Growth Repair Asexual reproduction Do we divide or multiply? A Mathematical Question • http://www.youtube.com/watch?v=nPG6480R Qo0&feature=related • http://www.youtube.com/watch?v=nPG6480R Qo0&NR=1 Dolly • Dolly was the first mammal to be successfully cloned. Snuppy Cloning gone very wrong… • Activities CELL DIVISION AND THE CELL CYCLE G0 cell that has exited the cell cycle – nerve cells are permanently here – they are unable to divide again • Drugs and alcohol kill brain cells- it’s not a myth DO NOT DO STUPID THINGS THAT KILL THEM • Actually, they kill all of your cells, brain cells just don’t grow back. Mitosis • • • M phase Period of nuclear division four phases Anaphase Metaphase Late Prophase Telophase & Cytokinesis Early Prophase Interphase (G1, S, G2) Cytokinesis • http://www.youtube.com/watch?v=4PKjF7Ou mYo&feature=player_embedded# CELL DIVISION STAGES Prophase • • • • • DNA coils into chromosomes Centrioles form Spindle fibers come from centrioles nucleolus and nuclear envelope disintegrated longest of the phases Prophase (early) Metaphase Anaphase Telophase and Cytokinesis 1 6 2 3 5 4 interphase EARLY prophase LATE prophase HOW DID YOU DO? metaphase anaphase interphase CANCER- THE BASICS CANCER WHAT CAUSES CANCER? A LOSS OF THE CONTROL MECHANISMS Basic definitions • Tumor: abnormal proliferation of cells that results from a loss of control of mitosis – Benign: pose no threat to the health of the individual provided that they do not get so large as to become a threat – Malignant: uncontrolled cell division that invades and destroys healthy tissue Basic definitions • Metastasis: spread of cancer cells beyond their original site – Allows the cancer to spread to other parts of the body Cancer and the cell cycle • Cancer cells divide even when there is inadequate room for new cells (hence a dense tumor) • Cancer cells divide when not attached to the body (hence metastasis) It typically takes multiple mutations to cause cancer. There is an entire spectrum of what cells may look like, from normal to invasive dysplasia. Metastasis EXAMPLES OF CANCER Lungs: non-smoker and smoker Smoking facts you should know…. • The average smoker decreases his or her lifespan by 17 years. • Almost all first use occurs before high school graduation. • Roughly 6 million teens in the US today smoke despite the knowledge that it is addictive and leads to disease. Facts you should know…. • Of every 100,000 15 year old smokers, tobacco will prematurely kill at least 20,000 before the age of 70. • Of the 3,000 teens who started smoking today, nearly 1,000 will eventually die as a result from smoking. Facts you should know…. • Although only 5 percent of high school smokers said that they would definitely be smoking five years later, close to 75 percent were still smoking 7 to 9 years later. Facts you should know…. • More than 90 percent of adult smokers started when they were teens. • The EPA has classified secondhand smoke as a carcinogen since 1992. • Every cigarette a man smokes reduces his life by 11 minutes. Each carton of cigarettes thus represents a day and a half of lost life. Every year a man smokes a pack a day, he shortens his life by almost 2 months. Facts you should know…. • Nine out of ten smokers say they want to quit. • Cigarettes are the single-most traded item on the planet, with approximately 1 trillion being sold from country to country each year. At a global take of more than $400 billion, it’s one of the world’s largest industries. Stages of Cancer • Stage I: tend to be small and localized; usually curable • Stage II: tend to be locally advanced • Stage III: tend to involve the local lymph nodes • Stage IV: metastasis • Each type of cancer has its own very specific guidelines for staging. Colon Cancer Rates of cancer • Regular screening by yourself or a doctor can sometimes help – Small tumors that have not yet metastasized are good candidates for surgical removal – Chemo therapy or radiation therapy is an attempt to kill the cancer cells before killing the patient. (Cells that are dividing are more susceptible to the affects than non-dividing cells.) Viruses and cancer • Certain viruses can cause cancer in plants and animals • Many viral genes are oncogenes • Viruses may suppress the tumorsuppressing genes Cancer • http://www.youtube.co m/watch?v=VlN7K19QB0&feature=related Cell Division For reproductive cells Meiosis I Meiosis II Prophase I • • • • chromosomes condense chromosomes arrange themselves with homolog tetrad: pair of homologous chromosomes crossing over may occur (later section) Metaphase I • • • spindle fibers attach from each pole tetrads line up along midline orientation of homologous pairs is independent and random Anaphase I • • chromosomes migrate to opposite poles cells now haploid Telophase I • • • chromosomes reach opposite poles and cytokinesis begins cells are not (necessarily) identical nuclear membranes form Meiosis II Prophase II • a. spindles reform Metaphase II • a. chromosomes line up along mid line Anaphase II • chromatids separate and move to opposite poles Telophase II • • nuclear membranes form cytokinesis occurs Video Formation of gametes • spermatogenesis – – – go through the above and form 4 useable cells sperm occurs in testes throughout adulthood of males Note the even distribution of cytoplasm Spermatogenesis Video Formation of gametes • oogenesis – eggs – a.k.a. ova (ovum- singular) – uneven cytokinesis results in one useful cell and 3 polar bodies – polar bodies degenerate and material can be used again Note the uneven distribution of cytoplasm Oogenesis • Compare Mitosis and Meiosis asexual reproduction • • • one parent genetically identical offspring budding Sexual reproduction • • • two parents genetically unique offspring increases variation Sexual Reproduction • http://www.youtube.com/watch?v=D1_mQS_FZ0 • http://www.youtube.com/watch?v=iCL6d0Ow Kt8&feature=related