CHAPTER 4 © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FORChromosomes SALE OR DISTRIBUTION NOT FOR SALE and OR DISTRIBUTION Sex-Chromosome© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC InheritanceNOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION CHAPTER OUTLINE Chromosomes come in pairs, one from the mother and the other from the father. Human cells have 23 pairs of 4.1 The Stability of Chromosome Complements chromosomes—46 chromosomes altogether. [© Hybrid Medical/Photo Researchers, Inc.] 4.2 Mitosis © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Meiosis 4.3 NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 4.4 Sex-Chromosome Inheritance 4.5 Probability in the Prediction of Progeny Distributions 4.6 Testing Goodness of Fit to a Genetic Hypothesis CONNECTION Grasshopper, Grasshopper E. Eleanor Carothers© Jones 1913 & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC The MendelianNOT Ratio FORin Relation SALE to Certain OR Orthopteran DISTRIBUTION Chromosomes NOT FOR SALE OR DISTRIBUTION CONNECTION The White-Eyed Male Thomas Hunt Morgan 1910 Sex-Limited Inheritance in Drosophila CONNECTION Seeds of Doubt © JonesRonald & Aylmer Bartlett Fisher Learning, 1936 LLC © Jones & Bartlett Learning, LLC Has Mendel’s Work Been Rediscovered? NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION. 26105_CH04_116_153.indd 116 4/27/11 9:32 AM © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION LEARNING OBJECTIVES & SCIENCE COMPETENCIES Understanding how© chromosomesJones & Bartlett and sex-chromosomes Learning, LLC are inherited as well as the© basicJones principles & Bartlett of probability Learning, LLC and statistical testsNOT of hypothesesFOR SALE discussed OR DISTRIBUTION in this chapter will allow you toNOT satisfy FOR the SALEfollowing OR science DISTRIBUTION competencies: ■ Predict what products of mitosis or meiosis would result from normal chromosome behavior or chromosome misbehavior. ■ Recognize the characteristic pattern of X-linked inheritance, and be able to trace X chromosomes as they pass ©between Jones the & sexesBartlett from Learning, generation toLLC generation. © Jones & Bartlett Learning, LLC ■ NOTGiven FOR a genetic SALE cross, OR use DISTRIBUTION the binomial distribution to calculate NOTthe probability FOR SALE of any OR particular DISTRIBUTION combination of genotypes or phenotypes among the progeny. ■ Be able to formulate a genetic hypothesis, use it to predict expected results of a cross, and compare the expected results with observed results by means of a chi-square test for goodness of fit. Interpret the results of the test © Jones & Bartlettaccording Learning, to whether LLC or not the hypothesis should© Jones be rejected. & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION t came as no great revelation that genes are located in chromosomes. The parallel Ibetween their properties© Jones made & Bartlett this quite Learning, LLC © Jones & Bartlett Learning, LLC obvious: NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 1. Genes come in pairs; chromosomes come in pairs. 2. Alleles of a gene segregate; homologous chromosomes segregate. 3.© UnlinkedJones & genes Bartlett undergo Learning, independent LLC © Jones & Bartlett Learning, LLC assortment; nonhomologous chromo- NOTsomes FOR undergo SALE independent OR DISTRIBUTION assortment. NOT FOR SALE OR DISTRIBUTION These parallels were first pointed out in MICROTUBULAR cytoskeleton of the African globe amaryllus (Scadoxus), which becomes transformed into the spindle in 1903, and after that time there was little doubt mitosis, as seen through a light microscope. [© Andrew S. that chromosomes are the cellular carriers of the Bajer/Bajer Research Projects.] © Jones &genes. Bartlett But parallels Learning, do not LLC constitute scientific © Jones & Bartlett Learning, LLC proof, nor does widespread agreement among years later, chromosomes were found to segregate NOT FORscientists. SALE ORIn this DISTRIBUTION chapter we shall examine some byNOT an orderly FOR SALEprocess OR into DISTRIBUTION the daughter cells of the experimental evidence that was at the formed by cell division as well as into the gametes time—and still is—regarded as sufficient to formed by the division of reproductive cells. prove the chromosome theory of heredity. Three important regularities were observed about © Jones & Bartlett Learning,the chromosome LLC complement (the© Jones complete & Bartlett Learning, LLC set of chromosomes) of plants and animals. 4.1 The StabilityNOT of Chromosome FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Complements 1. The nucleus of each somatic cell (a cell of the body, in contrast to a germ cell, The cell nucleus was first discovered in 1831, but or gamete) contains a fixed number of not until the late 1860s was it understood that chromosomes typical of the particular nuclear© Jones division &nearly Bartlett always Learning, accompanies LLC cell species. This© Jones number & variesBartlett tremen- Learning, LLC division. The importance of the nucleus in inheri- dously among species, and chromosome tanceNOT was reinforced FOR SALE by the OR nearly DISTRIBUTION simultaneous number bearsNOT little FOR relation SALE to theOR com- DISTRIBUTION discovery that the nuclei of two gametes fuse in plexity of the organism (TABLE 4.1). the process of fertilization. The next major 2. The chromosomes in the nuclei of advance came in the 1880s with the discovery of somatic cells are usually present in © Jones &chromosomes Bartlett Learning,, easily visualized LLC in the light © Jonespairs. &For Bartlett example, Learning, the 46 chromo-LLC microscope with the use of certain dyes. A few somes of human beings consist of 23 NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 4.1 The Stability of Chromosome Complements 117 © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION. 26105_CH04_116_153.indd 117 4/27/11 9:32 AM © Jones & BartlettTable 4.1 Learning,Somatic (diploid)LLC chromosome numbers of ©some Jones plant and & animalBartlett species Learning, LLC NOT FOR SALEOrganism OR DISTRIBUTION Chromosome numberNOT OrganismFOR SALE OR DISTRIBUTIONChromosome number Field horsetail 216 Yeast (Saccharomyces cerevisiae) 32 Bracken fern 116 Fruit fly (Drosophila melanogaster) 8 Giant sequoia 22 Nematode (Caenorhabditis elegans) 11 (, 12 & Macaroni wheat © Jones & Bartlett Learning, 28 LLC House fly © Jones & Bartlett 12 Learning, LLC Bread wheat NOT FOR SALE OR DISTRIBUTION 42 Scorpion NOT FOR SALE 4 OR DISTRIBUTION Fava bean 12 Geometrid moth 224 Garden pea 14 Common toad 22 Mustard cress (Arabidopsis thaliana) 10 Chicken 78 Corn (Zea mays) 20 Mouse 40 ©Lily Jones & Bartlett Learning, LLC 24 Gibbon © Jones & Bartlett Learning, 44 LLC NOTSnapdragon FOR SALE OR DISTRIBUTION 16 Human beingNOT FOR SALE OR DISTRIBUTION 46 pairs (FIGURE 4.1). Cells with nuclei that and the other from the paternal parent © Jones & Bartlett Learning,contain LLC two similar sets of chromo-© Jones & Bartlettof the Learning, organism. LLC somes are called diploid. A diploid 3. The gametes that unite in fertilization NOT FOR SALE OR DISTRIBUTIONindividual carries two alleleic copiesNOT ofFOR SALE toOR produce DISTRIBUTION the diploid somatic cells each gene present in each pair of chro- have nuclei that contain only one set of mosomes. The chromosomes occur in chromosomes, consisting of one mem- pairs because one chromosome of each ber of each pair. The gametic nuclei are ©pair Jones derives & fromBartlett the maternalLearning, parent LLC haploid. © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION FIGURE 4.1 Chromosome complement of a human male. There are 46 chromosomes, present in 23 pairs. At the stage of the division cycle in which these chromosomes were observed, each chromosome consists of two identical halves lying side by side longitudinally. Except for the members of one chromosome pair (the pair that determines sex), the members of all the chromosome © Jones & Bartlett Learning,pairs are the same LLC color because they contain DNA molecules© Jones that were& Bartlett labeled with Learning,the same mixture LLC of fluorescent dyes. The colors differ from one pair to the next because the dye