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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. 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 Copyright © 2009 Pearson Education, Inc. • 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 Prokaryote vs. Eukaryote Prokaryotic Cell Eukaryotic Cell Example: Bacteria E. coli Example: All Plant and Animal cells Lacks: A nuclear envelope/nucleus Contains: nucleus Lacks: nucleolus and other membranebound organelles Contains: nucleolus and membranebound organelles DNA present as: long circular molecule DNA present as: organized, extensively coiled structures. DNA does not: undergo extensive coiling DNA does: super coil into chromosomes fro cell division. Copyright © 2009 Pearson Education, Inc. Structure General Function Genetic Function Cell Membrane Defines and limits cell boundary to external environment Offers protection from mutations Glycocalyx Provides cell identity markers Provides genetic identity for chemical signaling Nucleus Houses and protects DNA from external environment Chromatin Uncoiled, functioning DNA; cell instructions for work Chromosomes Supercoiled/condensed structures that permit equal division of DNA during Mitosis and Meiosis Nucleolus Produces rRNA for use in gene expression (protein production) Cytoplasm Houses organelles; location of cell work Location for gene expression Endoplasmic reticulum (rough) Fold and process newly made proteins Translation of RNA to proteins Mitochondria Energy for cell work Energy for cell division and gene expression Chloroplast Traps sun energy to produce glucose Provides energy for plant cell division. Centrioles Produces spindle fibers for Mitosis and Meiosis Spindle Fibers Important in proper movement/separation of chromosomes during Mitosis and 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. Copyright © 2009 Pearson Education, Inc. Figure 2.3 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 23rd 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. Copyright © 2009 Pearson Education, Inc. Figure 2.4 Copyright © 2009 Pearson Education, Inc. Figure 2-4b Copyright © 2006 Pearson Prentice Hall, Inc. Haploid Number (n) • Equal to ½ of the diploid number. • Contains the genome of the species. Copyright © 2009 Pearson Education, Inc. Copyright © 2009 Pearson Education, Inc. Table 2.1