Cell Cycle, Mitosis, and Meiosis PDF

Cell Cycle, Mitosis and Meiosis Lab 04 Objectives: • Understand Cell cycle for eukaryotes • Understand the phases of mitosis • Understand the phases of meiosis Cell Cycle: Cell proliferation in Eukaryotic cells is regulated by a system called the cell cycle. This is not only governs how cells grow a...

Cell Cycle, Mitosis and Meiosis Lab 04 Objectives: • Understand Cell cycle for eukaryotes • Understand the phases of mitosis • Understand the phases of meiosis Cell Cycle: Cell proliferation in Eukaryotic cells is regulated by a system called the cell cycle. This is not only governs how cells grow and divide, but also has checkpoints to ensure that- at various stages- the correct events have taken place. Mitosis- a type of cell division in which one cell (the mother) divides to produce two new cells (the daughters) that are genetically identical to it. • prophase, metaphase, anaphase, and telophase. • Cytokinesis - the process of dividing the cell contents to make two new cells - starts in anaphase or telophase. General Biology BIO 101 Cell Cycle, Mitosis and Meiosis Lab 04 General Biology BIO 101 Cell Cycle, Mitosis and Meiosis Lab 04 At early G2 phase: By the start of G2 in the cycle, S phase is completed and the chromosomes have replicated. The cell is approaching the end of interphase. Although they have started to condense, individual chromosomes are not visible at this point. The chromosomes still exist as a mass chromatin within the nucleus. The centrosomes have replicated, and they begun to move forward opposite ends or poles of the cell. Late G2 phase: The cell has two centrosomes; each with two centrioles, and the DNA has been copied. At this stage, the DNA is surrounded by an intact nuclear membrane, and the nucleolus is present in the nucleus. Early prophase: The mitotic spindle starts to form, the chromosomes start to condense, and the nucleolus disappears. The chromosomes start to condense (making them easier to pull apart later on) Late prophase (prometaphase): The nuclear envelope breaks down and the chromosomes are fully condensed. The chromosomes finish condensing, so they are very compact. In animal cells, the replicated centrosomes migrate to opposite ends of the cell, establishing an axis for the organization of the spindle. Replicated chromosomes become attached to spindle fibers during prophase. General Biology BIO 101 Cell Cycle, Mitosis and Meiosis Lab 04 Metaphase During metaphase, the chromosomes migrate to the center of the cell. At the end of the metaphase, all chromosomes are aligned at the equator of the cell. Anaphase: During anaphase, the centrosomes of sister chromatids separate and are then pulled to opposite pole of the cell by mitotic spindle. The mitotic spindle grows in length causing the cell to elongate. General Biology BIO 101 Cell Cycle, Mitosis and Meiosis Lab 04 Telophase: In telophase, the chromosomes reach the pole of the cell, the chromosomes decondense, the mitotic spindle disintegrates and the nuclear envelope reforms. Cytokinesis in animal and plant cells: Cytokinesis in an animal cell: an actin ring around the middle of the cell pinches inward, creating an indentation called the cleavage furrow. Cytokinesis in a plant cell: the cell plate forms down the middle of the cell, creating a new wall that partition it in two. Meiosis- specialized form of cell division that produces reproductive cells, such as plant and fungal spores, sperm and egg cells. General Biology BIO 101 Cell Cycle, Mitosis and Meiosis Lab 04 An outline of meiosis: Meiosis is a reductive division which results in four haploid cells, each with one complete set of chromosomes, from a diploid cell. Meiosis consists of two rounds of division called meiosis I and meiosis II, with no DNA replication between divisions. The reduction in chromosome number occurs in the first meiotic division, or meiosis I. The homologous pairs of replicated chromosomes separate, halving the chromosome number. During meiosis I, the chromatids of homologous chromosomes exchange segments. This creates variation by producing chromosomes with new combinations of genetic material. Each division in meiosis consists of the same four stages that occur in mitosis: prophase, metaphase, anaphase and telophase. The stages of meiosis: Meiosis I - Prophase I, Metaphase I, Anaphase and Telophase I Meiosis II - Prophase II, Metaphase II, Anaphase II and Telophase II Meiosis I General Biology BIO 101 Cell Cycle, Mitosis and Meiosis Lab 04 Meiosis II Summary: Property DNA replication Number of divisions Synapsis of homologous chromosomes Number of daughter cells and genetic composition Role in the animal body Mitosis Occurs during interphase before mitosis begins Meiosis Occurs during interphase before meiosis I begins One, including prophase, metaphase, anaphase, and telophase Does not occur Two, each including prophase, metaphase, anaphase, telophase. Two, each diploid (2n) and genetically identical to the parent cell Enables multicellular adult to arise from zygote; produces cells for growth, repair, and in some species, asexual reproduction General Biology BIO 101 Occurs during prophase I along with crossing over between nonsister chromatics; resulting chisamata hold pais together due to sister chromatid cohesion. Four, each haploid (n) containing half as many chromosomes as the parent cell; genetically different from the parent cell and from each other. Produces gametes; reduces number of chromosomes by half and introduces genetic variability among the gametes. Cell Cycle, Mitosis and Meiosis Lab 04 Further reading: Campbell, N. A., Reece, J. B., Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V. and Jackson, R. B. (2008) Biology (8th edition). Published by Pearson Education. ISBN-13: 978-0321536167. Chapter 12 (The Cell Cycle) General Biology BIO 101