Copyright 2009 Pearson Education, Inc. Concepts of Genetics Seventh Edition Klug, Cummings, Spencer, Palladino Chapter 2 Mitosis and Meiosis Copyright 2009 Pearson Education, Inc. Introduction Every living thing, except some viruses, contains DNA as the genetic material that houses the information to control cell structure and function. A molecule of DNA is organized into units called genes; the products of gene expression direct the metabolic activity of cells. Copyright 2009 Pearson Education, Inc. Introduction DNA is also organized into chromosomes which serve as the vehicles for transmitting genetic information. Chromosomes are only visible during mitosis and meiosis. During interphase DNA is organized as chromatin. Copyright 2009 Pearson Education, Inc. Mitosis Leads to the production of two new cells, each with the same number of chromosomes as the original parent cell. Occurs in Somatic (body) cells. Copyright 2009 Pearson Education, Inc. Meiosis Reduces the genetic content and the number of chromosomes precisely in half. This reduction is essential if sexual reproduction is to occur without doubling the amount of genetic information in each generation. Occurs in Gametic/Germ line (sex) cells. Copyright 2009 Pearson Education, Inc. Figure 2.1 Copyright 2009 Pearson Education, Inc. Figure 2.2 Copyright 2009 Pearson Education, Inc. Prokaryote vs. Eukaryote Prokaryotic CellEukaryotic Cell Example: Bacteria E. coli Example: All Plant and Animal cells Lacks: A nuclear envelope/nucleusContains: nucleus Lacks: nucleolus and other membrane- bound organelles Contains: nucleolus and membrane- bound organelles DNA present as: long circular moleculeDNA present as: organized, extensively coiled structures. DNA does not: undergo extensive coilingDNA does: super coil into chromosomes fro cell division. Copyright 2009 Pearson Education, Inc. StructureGeneral FunctionGenetic Function Cell MembraneDefines and limits cell boundary to external environment Offers protection from mutations GlycocalyxProvides cell identity markersProvides genetic identity for chemical signaling NucleusHouses and protects DNA from external environment ChromatinUncoiled, functioning DNA; cell instructions for work ChromosomesSupercoiled/condensed structures that permit equal division of DNA during Mitosis and Meiosis NucleolusProduces rRNA for use in gene expression (protein production) CytoplasmHouses organelles; location of cell workLocation for gene expression Endoplasmic reticulum (rough) Fold and process newly made proteinsTranslation of RNA to proteins MitochondriaEnergy for cell workEnergy for cell division and gene expression ChloroplastTraps sun energy to produce glucoseProvides energy for plant cell division. CentriolesProduces spindle fibers for Mitosis and Meiosis Spindle FibersImportant in proper movement/separation of chromosomes during Mitosis and Meiosis. Copyright 2009 Pearson Education, Inc. 2.2: Chromosomes Exist in Homologous Pairs in Diploid Organisms Each chromosome contains a constricted region called the centromere; this provides a general appearance of each chromosome. p-arm: short arm p = petite Located above the centromere q-arm: long arm Located below the centromere Copyright 2009 Pearson Education, Inc. Figure 2.3 Copyright 2009 Pearson Education, Inc. Diploid Number (2n) Found in Somatic cells; contains the genome for an organism. Homologous chromosomes: each pair of matching chromosomes with identical size, shape, and centromere location. Contains identical genes. Locus: gene location; each chromosome has several loci along its length. In humans, all chromosomes EXCEPT sex chromosomes (the 23 rd pair) are homologous. Alleles: alternate forms of a gene; options. Copyright 2009 Pearson Education, Inc. Term Example Copyright 2009 Pearson Education, Inc. Karyotype Photograph of Mitotic chromosomes to examine for chromosomal aberrations. Sister Chromatids: parallel structures. Copyright 2009 Pearson Education, Inc. Figure 2.4 Copyright 2009 Pearson Education, Inc. Figure 2-4b Copyright 2006 Pearson Prentice Hall, Inc. Copyright 2009 Pearson Education, Inc. Haploid Number (n) Equal to of the diploid number. Contains the genome of the species. Copyright 2009 Pearson Education, Inc. Table 2.1