Download Mitosis and Meiosis - Lecture Slides | SOCR 330 and more Study notes Genetics in PDF only on Docsity! 1/20/2017 1 Chapter 2 “Mitosis and Meiosis” • Cell structure • Homologous chromosomes • Mitosis and cell division • Cell cycle control • Meiosis and sexual reproduction • Spermatogenesis and Oogenesis • Significance of meiosis Genetic continuity between cells and organisms of any sexually reproducing species is maintained by the processes of mitosis and meiosis. The processes are orderly and efficient, serving to produce diploid somatic cells and haploid gametes, respectively. It is during these division stages that the genetic material is condensed into discrete, visible structures called chromosomes. Cell Structure and Genetic Material 1. Eukaryotes (DNA) 2. Prokaryotes (DNA) 3. Viruses (DNA or RNA) 1/20/2017 2 Eukaryotes The term "eukaryote" comes from the Greek and means "true nucleus." Eukaryotic cells have a double membrane: Cell Membrane Nuclear membrane Cell Structure Eukaryotes = Higher organisms, having true nuclei and membranous organelles whose cells demonstrate mitosis and meiosis. Usually multi-cellular and having a more complex life cycle than prokaryotes. http://tolweb.org/Eukaryotes Eukaryota: Organisms with nucleated cells Eukaryotic generalized cell structure 1/20/2017 5 Karyotype of Human Chromosomes Is this a male or female? Chromosome Structure Chromosome Morphology Notice that every chromosome doubles during cell division and can be seen as a pair of chromatids still connected at the centromere during late prophase and metaphase. 1/20/2017 6 Chromosome number varies among organisms. Cell division Cell Division and the Cell Cycle Why do cells divide? How many cells in our body? (~50 trillion) Where do cells divide? How do cells divide? 1/20/2017 7 Do all cells divide continuously? Only some cells go on to divide repeatedly, most mature (differentiate) into functioning cells: Liver cells Brain cells Skin cells Colon, stomach, etc. The Cell Cycle Genes regulate the Cell Cycle. How long does cell division take? Example here for human cells in culture. 1/20/2017 10 Meiosis = sexual cell division Leads to production of sperm and egg. Meiosis I (aka. reductional division) Prophase I Metaphase I Anaphase I Telophase I Meiosis II (aka. equational division) Prophase II Metaphase II Anaphase II Telophase II 1/20/2017 11 Prophase I - Homologous chromosomes pair and condense Meiosis I Meiosis II 1/20/2017 12 Meiosis I and Meiosis II Together Mitosis vs Meiosis 2n 2n 2n n Spermatogenesis vs Oogenesis Spermatogenesis (male) Meiosis results in four sperm or pollen grains for each spermatagonium Oogenesis (female) Meiosis results in only one egg for each primary gametocyte
