Chapter 4 The Chromosome Theory of Inheritance 4-1
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Sections to study4.1 Chromosomes: The carriers of genes4.2Mitosis:Cell division thatpreserves chromosomenumber4.3 Meiosis: Cell division that halve chromosome number4.4Gametogenesis4.5Validation of the chromosome theory4-2
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 4-2 Sections to study Sections to study 4.1 Chromosomes: The carriers of genes 4.1 Chromosomes: The carriers of genes 4.2 Mitosis: Cell division that preserves chromosome 4.2 Mitosis: Cell division that preserves chromosome number 4.3 Meiosis: Cell division that halve chromosome number 4.3 Meiosis: Cell division that halve chromosome number 4.4 Gametogenesis Gametogenesis 4.5 Validation of the chromosome theory 4.5 Validation of the chromosome theory
Chromosome4.1 Chromosomes:ChranChrcmatidNucleurTekomereThe carriers ofCentromeregenesTelomoreCellBase PairsNA(doubie helix
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 4-3 4.1 Chromosomes: 4.1 Chromosomes: The carriers of The carriers of genes
1667-Anton van LeeuwenhoekSemen contains spermatozoa ("sperm animals")Hypothesized that sperm may enter egg to achieve fertilization1854-1874-confirmationoffertilization through union ofeggsand spermsObserved fertilization in frogsand sea urchins using microscopyThe nucleiare the only elementscontributed equallyby spermsand eggs.4-4
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 4-4 1667 – Anton van Leeuwenhoek Anton van Leeuwenhoek Semen contains Semen contains spermatozoa spermatozoa (“sperm animals sperm animals”) Hypothesized that sperm may enter egg to achieve fertilization. Hypothesized that sperm may enter egg to achieve fertilization. 1854-1874 – confirmation of confirmation of fertilization through union of fertilization through union of eggs and sperms eggs and sperms Observed fertilization in frogs Observed fertilization in frogs and sea urchins using microscopy. and sea urchins using microscopy. The nuclei are the only elements The nuclei are the only elements contributed equally by sperms contributed equally by sperms and eggs. and eggs
Evidence that genes reside in chromosomes1880s-innovations in microscopy and stainingtechniques identified thread-like structures:chromosomes(coloredbodies")4-5Fig.4.8
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 4-5 Evidence that genes reside in chromosomes Evidence that genes reside in chromosomes 1880s – innovations in microscopy and staining innovations in microscopy and staining techniques identified thread techniques identified thread-like structures: like structures: chromosomes chromosomes (“colored bodies colored bodies”). Fig. 4.8
Tracking the movement of chromosomes during celldivision.Somatic cells undergo mitosis - one type of nuclear divisionthat results in two daughter cells containing same number andtype ofchromosomes asparent cells.Germ cells undergo meiosis-one type of nuclear division thatresults in daughter cells containing half the number ofchromosomesastheparents.4-6
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 4-6 Tracking the movement of chromosomes during cell Tracking the movement of chromosomes during cell division. division. Somatic cells undergo Somatic cells undergo mitosis mitosis – one type of nuclear division one type of nuclear division that results in two daughter cells containing same number and that results in two daughter cells containing same number and type of chromosomes as parent cells. type of chromosomes as parent cells. Germ cells undergo Germ cells undergo meiosis meiosis – one type of nuclear division that one type of nuclear division that results in daughter cells containing half the number of results in daughter cells containing half the number of chromosomes as the parents. chromosomes as the parents
Haploid vs diploid cellsDrosophilamelanogasteGamete contains one-half thenumber of chromosomes asthezygote.Haploid-cells that carry only aCsingle chromosome setDiploid- cells that carry twomatching chromosome setsn-the number of chromosomes inDiploidcells2n=8a haploid cell2n-thenumberofchromosomesina diploid cellAtfertilization,haploid gametesHaploid cells(gametes)n=4produce diploid zygotesFig.4.24-7
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 4-7 Haploid Haploid vs diploid cells diploid cells Gamete contains one Gamete contains one-half the half the number of chromosomes as the number of chromosomes as the zygote. zygote. Haploid Haploid – cells that carry only a cells that carry only a single chromosome set single chromosome set Diploid Diploid – cells that carry two cells that carry two matching chromosome sets matching chromosome sets n – the number of chromosomes in the number of chromosomes in a haploid cell a haploid cell 2n – the number of chromosomes in the number of chromosomes in a diploid cell a diploid cell At fertilization, haploid gametes At fertilization, haploid gametes produce diploid zygotes. produce diploid zygotes. Fig. 4.2
The numberand shape of chromosomesvaryfrom speciesto species2nOrganismn84Drosophila melanogaster510Drosophila obscura612Drosophila virilus714Peas1428Macaroni wheat1122Giant sequoia trees4794Goldfish3978Dogs4623Humans4-8
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 4-8 The number and shape of chromosomes The number and shape of chromosomes vary from species to species vary from species to species Humans 23 46 Dogs 39 78 Goldfish Goldfish 47 94 Giant sequoia trees Giant sequoia trees 11 22 Macaroni wheat Macaroni wheat 14 28 Peas 7 14 Drosophila Drosophila virilus virilus 6 12 Drosophila Drosophila obscura obscura 5 10 Drosophila melanogaster Drosophila melanogaster 4 8 Organism Organism n 2n
Anatomy of a chromosomePairofhomologousPairofhomologousmetacentricchromosomesacrocentricchromosomesCentromereCentromereSisterNonsisterchromatidschromatidsNonhomologouschromosomesHomologouschromosomesHomologouschromosomes4-9Fig.4.3
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 4-9 Anatomy of a chromosome Anatomy of a chromosome Fig. 4.3
Homologouschromosomes (homologs)Each pair matches in size,shape,and banding patternContain the same set of genesGenes may carry different alleles.Nonhomologous chromosomes carry completelyunrelated sets ofgenes4-10
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 4-10 Homologous chromosomes ( Homologous chromosomes (homologs homologs) Each pair matches in size, shape, and banding pattern. Each pair matches in size, shape, and banding pattern. Contain the same set of genes. Contain the same set of genes. Genes may carry different alleles. Genes may carry different alleles. Nonhomologous Nonhomologous chromosomes carry completely chromosomes carry completely unrelated sets of genes. unrelated sets of genes