Variations on a Theme Species Characteristics What characteristics are Shared by each of these Species? Individual characteristicsmake a person unique Although your genes carry your master plan there are other factors that make you YOU! Like What? Environment Spiritual life GeneticsThe Study of Heredity Genes A section of DNA that codes for a particular trait (the recipe for a protein) Chromosomes Threadlike structures composed of DNA and proteins found in the nucleus of the cell. • Chromatid- one of the identical halves of the chromosome • Centromereconstricted area where chromatids are joined Homologous Pairs and Homologues MITOSIS MEIOSIS • Diploid- has two of each chromosome2n- product of mitosis • Haploid- 1 of each chromosome- 1nproduct of meiosis Humans have 46 chromosomes or 23 pairs of chromosomes Fruit Flies 8 chromosomes or 4 pairs Goldfish • 100 chromosomes or 50 pair Crayfish • 200 chromosomes or 100 pair Lilies, Tomatoes, White Pines • All have 24 chromosomes or 12 pair • It’s not the chromosome number that determines the species but the genes on the chromosomes What is a Karyotype? • • A photograph or stained, separated and sorted chromosomes How many chromosomes would there be in a human diploid cell? A haploid cell? Haploid cells are for reproduction What is the difference between a gene and a chromosome? Cell Division And the Cell Cycle What is the cell cycle? The life cycle of a cell Interphase Prophase Mitosis Cytokinesis Mitosis • The division of a cell to produce two identical daughter cells Interphase •Chromosomes are copied •Appear as “threadlike”coils (chromatin)at the start, but each chromosome and its copy (sister chromosome) change to sister chromatids at end of this phase. •Chromatid Prophase •Mitosis begins •Centrioles appear •Spindle fibers form between the poles Metaphase •Chromatids attach to spindle fibers in center Anaphase •Chromatids separate and begin to move to opposite sides of the cell Telophase •Two nuclei form •Chromosomes appear as chromatin (threads rather than rods •Mitosis ends Cytokinesis •Membrane moves inward to create two daughter cells with identical chromosomes Prophase Whitefish Onion Metaphase Whitefish Onion Anaphase Whitefish Onion Telophase Whitefish Onion All Together Now Uses of Mitosis • Growth • Repair and replace old or damaged cells • Asexual reproduction Forming Gametes for Sexual Reproduction MEIOSIS Who discovered meiosis? Van Beneden Studying Ascaris Meiosis Vocabulary • Zygote- a diploid cell formed by the union of a haploid sperm and egg • Meiosis- the forming of sexual gametes by reducing the number of chromosomes from diploid to haploid through two divisions. Meiosis- two divisions • 1st division reduces the # of chromosomes from diploid to haploid • 2nd division doubles the number of cells Meiosis Comparison of Mitosis and Meiosis Compare Metaphase: Mitosis Metaphase Meiosis Metaphase I Compare Anaphase Mitosis Anaphase Meiosis Anaphase I Compare Daughter Cells Produced: Mitosis Meiosis Purpose of Meiosis • To form gametes for sexual reproduction • Four viable sperm are produced from spermatogenesis • One viable egg produced from oogenesis Meiosis Vocabulary • Gameteshaploid cells that, when united, form a diploid zygoteex. sperm, eg Meiosis Vocabulary • Fertilization- the process of forming a zygote Meiosis Vocabulary • Spermmale gamete • Eggfemale gamete Meiosis Vocabulary Forming of Sperm Forming of Eggs Meiosis Vocabulary • Sexual Reproduction-The fertilization (union) of haploid gametes to produce offspring that are not genetically identical to either parent