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BIO 1B UNIT GOALS Identify that cells dividing for growth and repair go through mitosis. Identify that cells dividing to produce sex cells go through meiosis. Draw a diagram of mitosis and mitosis that shows the differences in chromosome number in the daughter cells. Compare the advantages and disadvantages of sexual and asexual reproduction. Describe how genetic recombination through meiosis and crossing over increases variation. Describe how stem cells differentiate to become the many different cells in your body. Identify a normal karyotype of a human cell as having 23 pairs of chromosomes Identify karyotypes that are not normal and locate the chromosomal abnormality Write how a particular type of cancer happens Write why cancer makes people sick CELL SIZE/ GROWTH Each organism starts as one cell. Organisms grow when cells divide and make more cells. Cells use diffusion to get materials in an out of the cell. It is more efficient to distribute materials throughout a smaller cell than a larger cell because smaller cells have a larger surface area to volume ratio. GROWTH CON’T When examining why multi-cellular organisms made of many small cells instead of one large cell it is useful to use potato cubes as a model. The following diagrams represent potato cubes of different sizes (3 cm, 2 cm, 1 cm) that were soaked in iodine overnight. The next day we removed the cubes from the iodine and sliced them in half to show how far the iodine entered the cube. Length of side Surface Area Volume of of cube Cube to Volume Ratio 3cm 9*6 = 54 cm2 27 cm3 54 : 27 or 2:1 2cm 4*6 = 24 cm2 8 cm3 24:8 or 3:1 1cm 1*6 = 6 cm2 6:1 1 cm3 BIG IDEA The smallest cube (1cm X 1cm X 1cm) has the largest surface area to volume ratio. Sexual vs. Asexual reproduction In Asexual Reproduction a single parent produces one or more identical offspring by dividing into two cells. Many single celled organisms like bacteria reproduce asexually making duplicate copies of themselves. Most plants are also able to reproduce asexually. Sexual Reproduction involves two parents giving rise to offspring that have unique combination of genes inherited from the two parents. This usually involves the combination of two different forms of gametes like eggs and sperm. In both sexual and asexual reproduction genetic material is passed on to the offspring. Asexual Reproduction Advantages Produce more offspring Only one parent is required All of that parent's genes are passed on to its offspring Do not have to waste energy or exposure to predators by seeking mates. Sexual Reproduction Advantages Increases the rate of beneficial (helpful) mutations in a population. Increases genetic variety and gene combination increasing a population’s chance for survival. The increase in genetic variety increases a population’s ability to fight off disease. Cell Theory includes the following tenants: Cell Theory All organisms are composed of one or more cells. The cell is the basic unit of structure and organization of organisms. All cells come from pre-existing cells. Cells contain hereditary information that is passed from cell to cell during cell division All cells are basically the same in chemical composition and metabolic activities Bell work 12.7.11 WHY IS IMPORTANT THAT CELLS STAY SMALL? 2. WHICH SURFACE AREA TO VOLUME RATIO IS MORE BENEFICIAL TO CELLS 3:1 OR 6:5 AND WHY? 3. WHAT ARE THE DIFFERENCES BETWEEN ASEXUAL AND SEXUAL REPRODUCTION? 4. LIST ONE TYPE OF ORGANISM THAT REPRODUCES ASEXUALLY. 1. Mitosis and Meiosis http://www.cellsalive.com/meiosis.htm Mitosis Produces the somatic, or body cells necessary for growth Results in diploid cells with the same number of chromosomes as the parent cell Produces 2 daughter cells with genetic material that is identical to parent cell Unicellular organisms use mitosis to reproduce. They remain unicellular, but with two organisms instead of 1. Meiosis Produces the gametes or sex cells like eggs, sperm, and spores. Results in haploid cells with half the number of chromosomes as the parent cells Passes on half of the genetic material of the parent cell CHROMOSOMES Chromosomes are contained in the nucleus. They contain the genetic code in the form of genes. Genes are a unit of heredity made of DNA. In discussions of cell division the genetic material is referred to as chromosomes when it is visible and ready to duplicate. Otherwise it is called chromatin. Chromosomes are counted based on the number of centromeres, not the number of chromatids. Homologous Chromosomes are pairs of similar chromosomes. They have the same length and centromere location. Humans receive one chromosome from each parent. Each chromosome contains genes that code for the same set of traits. However the version of the trait that you get from each parent may be different on each chromosome so homologous chromosomes are similar but not identical. Bell work 12.8.11 – Thursday WHERE CAN CHROMOSOMES BE FOUND? WHAT DO THEY CONTAIN? 2. WHAT IS THE CORRECT NUMBER OF CHROMOSOMES A BODY CELL (SOMATIC) SHOULD HAVE? 3. HOW MANY CHROMOSOMES SHOULD A GAMETE HAVE (SPERM/ EGG)? 1. Diploid cells are referred to as 2n. The chromosomes appear as homologous pairs. This is the normal amount of chromosomes in cells. Haploid cells are referred to as n. There is only one of each chromosome from either the mother or the father. This is half of the normal amount of chromosomes in cells. MEIOSIS Human body cells: Have 46 chromosomes or 23 pairs This is described as n= 23 and 2n= 46 Our somatic cells have 46 chromosomes (ex: Human Skin Cell) Our gamete cells have 23 chromosomes (ex: Human Sperm Cell) In Mitosis the chromosome number is conserved throughout the process. The genetic material doubles during the process when each chromatid replicates to make an identical sister chromatid. Then the sister chromatids split into two separate cells. Throughout the process the chromosome number stays the same since it is based on the number of centromeres not on the number of chromatids. . The diagram below is based on a fruit fly which has 8 chromosomes or 4 pairs of chromosomes in a somatic cell. Please note that during Mitosis the homologous pairs do not line up as diagrammed below. This diagram simply shows how the chromosome number is determined. CELL DIFFERENTIATION The cells differentiate into specific cells with specialized functions. Following fertilization, cell division produces a small cluster of cells. Early embryo cells can become any cell type and are referred to as totipotent. http://player.discoveryeducation.com/index.cfm?guid AssetId=7090CF16-CDA8-4004-A13ED07E2CD59AA9&blnFromSearch=1&productcode=US # CELL DIFFERENTIATION This totipotency lasts for about 14 days or until there are about 16 cells in the embryo. After this, gastrulation occurs where the embryonic cells start to divide into germ cell layers. At this point cells differentiate by appearance and function. CELL DIFFERENTIATION How a cell is specialized, or differentiated, depends on its position in the embryo. Neighboring cells will send chemical cues. These chemicals signal genetic switching on or off of genes within the cell. Karyotypes Karyotypes Karyotypes help geneticists to diagnose chromosomal abnormalities. A karyotype is a picture of the paired up chromosomes. To prepare a karyotype, scientists add colchicine, a drug that interferes with the spindle fibers, which stops all cell division at metaphase. Water is then added which causes the cells to burst. The burst cells are stained and examined under a microscope. A digital picture is taken of the chromosomes stuck in Metaphase. Scientists use a computer to cut out the individual chromosomes and pair them up. Chromosomes of the same size and similar looking bands are paired according to their centromere position. From the karyotype, certain abnormalities, such as an extra chromosome or piece of chromosome, can be detected. Normal Male copyright cmassengale 2n = 46 30 Normal Female copyright cmassengale 2n = 46 31 Male, Trisomy 21 (Down’s) copyright cmassengale 2n = 47 32 Female Down’s Syndrome copyright cmassengale 2n = 47 33 Female Down’s Syndrome copyright cmassengale 2n = 47 34 Klinefelter’s Syndrome copyright cmassengale 2n = 47 35 Turner’s Syndrome 2n = 45 copyright cmassengale 36 Karyotype Questions 1. 2. 3. 4. 5. What is a karyotype? What is the difference between a females a karyotype and a males karyotype? What is Down’s Syndrome? What is Kleinfelter’s Syndrome? What is Trisomy 13 Syndrome? Bell work 12.12.11 MONDAY WHAT IS A KARYOTYPE? 2. WHAT ARE THE BENEFITS OF A KARYOTYPE? 3. EXPLAIN HOW YOU CAN DIFFERENTIATE A MALE AND FEMALE BY LOOKING AT A KARYOTYPE? 1. CANCER http://www.youtube.com/watch?v=WXTsxPPcTEs Enzymes, which are a type of protein, control the cell division. Genes direct the production of proteins including enzymes. DNA Mutations can occur in genes that produce those enzymes and control cell division. If this happens cells can grow, divide, and reproduced rapidly. This uncontrolled cell division is called cancer. HOW DO WE DIE FROM IT?? These excess cells cause tumors that starve the surrounding cells making a person sick. In later stages of cancer, cancerous cells may break away, enter the bloodstream and affect other parts of the body (metastasis) Causes of Cancer Environmental mutagens increase mutations and therefore increase the chance of cancer. Viruses change cells’ DNA by integrating their genetic material with the host cell's DNA. Mutations that cause uncontrolled cell division can be inherited and passed down through the sex cells. Most cancers are thought to be multi-factorial and caused by both environmental and genetic factors. 12.13.11 TUESDAY BELL WORK WHAT IS CANCER? HOW DOES IT EFFECT SURROUNDING CELLS? 2. WHAT DOES THE TERM METASTASIS MEAN? 3. WHAT ARE TWO WAYS SOMEONE CAN GET CANCER? 1. Genetic Mutations http://www.youtube.com/watch?v=FgMKGIED4Yo Mutations are changes in the DNA sequence REAL LIFE: HOUSE MUTATED TO HOOUSE, HOUSE TO HORSE, HOUSE TO HOUE Mutations occur in both sex cells and body cells. Passing on Mutations An altered gene (mutation) may be passed on to every cell that develops from it. EXAMPLE: OUR SKIN CELLS DIE BUT THAT TATOO STAYS INTACT. GENETIC MUTATIONS If a mutation is a sex cell, like a sperm or an egg, and if that sex cell goes through fertilization then the mutation will be passed on to the offspring. IF YOU GET A TATOO ON YOUR ARM WILL YOUR BABY BE BORN WITH A TATOO ON IT’S ARM? Mutations in body cells are not passed on to offspring. However the mutation may cause problems for the individual. CELLS OF THE LUNG THAT GET CANCER FROM CIGARETTE SMOKE- CAN EFFECT OTHER CELLS. Causes of Mutations Spontaneous mutations happen as a mistake in base pairing. (THINK OF TYPING/ TEXTING AND MAKING MISTAKES) Mutagens – certain chemicals and environmental hazards may change the structure of DNA, and therefore may alter the proteins coded by that DNA . Radiation (X-rays, cosmic rays, UV light, Nuclear) breaks apart DNA can result in deletions. Chemical Mutagens (asbestos, formaldehyde) usually cause substitution mutations.