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Summer BIO 152F How do cells divide? mitosis and meiosis Lectures 9&10 May 31st 2005 Outline • Context and connectionsevolution & genetics • Prokaryotic cell division • Eukaryotic cell division: – Mitosis – Meiosis 1 Cornerstone of evolution Inheritance of variable traits leading to a difference in reproductive success. All organisms are related-- common ancestry Organisms have changed over time [Cell theory pattern and process] All organisms composed of cells and cells arise from other cells 2 Ultimate questions & explanations = WHY? (Evolutionary context) Proximate questions & explanations= HOW? (includes what, where, when) Proximate explanation Variability Inheritance 3 Topics What is the hereditary material? How is the hereditary material duplicated? How is the hereditary material passed on to the next generation? How is variation generated? Working backwards First, we will look at cells. Common features Differences 4 Cell types—Fig 1-5 Prokaryote Eukaryote Note the difference in size and structure Prokaryotes are smaller and do not have a nucleus Cell division In unicellular organisms, cell division equals reproduction. In multicellular organisms, cell division is important in the growth and maintenance of tissues as well as in reproduction. Process works best when new cells are an exact copy of the old. But this process does not always proceed according to plan….. 5 Bacterial cell division • Fig 11-6 Eukaryotic cells divide by mitosis and meiosis. The CELL CYCLE is regulated, including entry into mitosis. Entry into meiosis is also regulated. Next few slides were from text: 11.16 cell cycle 11.7 closer look at chromosomes 11.8 overview of mitosis 11.9 mitosis and cytokinesis 6 Mitosis-ultimate questions What is the significance of mitosis? Heritability Variability What is the consequence of error? Reproduction • Of eukaryotic organisms • (We will look at prokaryotic organisms Thursday) 7 Eukaryotic life cycle haploid (1n) Meiosis Fertilization diploid (2n) Meiosis: the reduction process in which a diploid cell produces four haploid cells over two divisions Overview of important steps Figures-12.3; 12.4 [you learn the steps I will focus on the significance to variation and inheritance] 8 Summary Prokaryotes have a simple mode of cell division - no mitosis or meiosis In eukaryotes, mitosis results in cells that are identical or nearly so. In meiosis, homologous chromosomes pair and exchange segments (genetic recombination). Chromosome content is halved. Meiosis: ultimate questions What is the significance of meiosis? Heritability Variability What is the consequence of error? 9 Bacteria-lab 3 Useful readings in the text: Bacterial diseases- pp583-84 (Chap 27) Essay Antibiotics and evolution of resistance Reproduction and inheritance: Box 27.1 Box 19.1 (plasmids—including Fig 19.2) Also- essay p 358 Ch 16 antibiotics that poison the ribosome Lateral gene transfer p432 Readings for this section Chapter 12—all Chapter 11 pp227 -230; 11.2 (pp 232-236) More readings about mutation later Basic genetics-Chapter 13 (some sections) 10 How do you study this? NOW: Make a list of important terms-know what they are and how they are connected. Learn the stages of mitosis & meiosis Know how they are similar, different, when they occur, By the end know the consequence of error at each step 11