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UNT BIOL 3451 - Introduction to Genetics/ Meiosis and Mitosis
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BIOL 3451 1st Edition Lecture 2 Outline of Last Lecture I. 1.1 Genetics Has a Rich and Interesting HistoryII. 1.2 Genetics Progressed From Mendel to DNA in Less Than a CenturyIII. 1.3 Discovery of the Double Helix Launched the Era of Molecular GeneticsIV. 1.4 Development of Recombinant DNA Technology Began the Era of CloningV. 1.5 The Impact of Biotechnology Is Continually ExpandingOutline of Current Lecture I. 1.6 Genomics, Proteomics, and Bioinformatics Are New and Expanding FieldsII. 1.7 Genetic Studies Rely on the Use of Model OrganismsIII. 1.8 We Live in the Age of GeneticsIV. Chapter 2: Mitosis and MeiosisV. 2.1 Cell Structure Is Closely Tied to Genetic FunctionVI. 2.2 Chromosomes Exist in Homologous Pairs in Diploid OrganismsVII. 2.3 Mitosis Partitions Chromosomes into Dividing CellsVIII. 2.4 Meiosis Reduces Chromosome # from Diploid to Haploid in Germ Cells and SporesCurrent LectureI. 1.6 Genomics, Proteomics, and Bioinformatics Are New and Expanding Fields• Genomics: analyzes genome sequences to study the structure, function, and evolution of genes and genomes• Proteomics: identifies a set of proteins present in cells under a given set of conditions and studies their post-translational modifications, their locations within cells, and their interactions• Lateral transmission: helps spread of genes (doesn’t come from parents, but cousins)• Bioinformatics: stores, retrieves, and analyzes data generated by genomics and proteomics• All life has a common origin• genes with similar functions in different organisms are similar in structure and DNA sequenceII. 1.7 Genetic Studies Rely on the Use of Model OrganismsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.• Criteria for model organisms in genetics:– easy to grow– short life cycle – produce many offspring• Recombinant DNA technology (transfer genes across species)– Allowed us to develop models of human diseases to study (Table 1.2)III. 1.8 We Live in the Age of Genetics• Mendel began study of genetics and now at Human Genome Project• Numerous Nobel Prizes have been awarded in the field of genetics• Lots of ethics issues around genetics• prenatal testing• ownership of genes (not so much anymore because can’t patent a gene)• access to/safety of gene therapyIV. Chapter 2: Mitosis and Meiosis• Eukaryotes: mitosis and meiosis are necessary for reproduction• Meiosis: production of gametes • Mitosis: production of two genetically identical cellsV. 2.1 Cell Structure Is Closely Tied to Genetic Function• Cell structure is closely tied to genetic function• Two main types of cells • Prokaryotic (bacteria, archaea)• Eukaryotic (protists, plants, fungi, animals)• Difference between two is Eukaryotes membrane-bound structures• All cells share some common features:• Plasma membrane• DNA• Ribosomes• Cell surrounded by plasma membrane• Plants: cell wall made of cellulose • Bacteria: have peptidoglycan on their cell wall• DNA in nucleus: has acidic and basic proteins (more proteins) as fibers• Higher eukaryotes: just because the genes are there, doesn’t mean they work• During nondivisional phases of the cell cycle, these fibers are uncoiled and dispersed into chromatin and then condense to form chromosomes during mitosis and meiosis• Centrioles are located in centrosome in animal cells• Form spindle fibers for movement of chromosomesVI. 2.2 Chromosomes Exist in Homologous Pairs in Diploid Organisms• Chromosomes exist in homologous pairs in diploid organisms• Somatic cells (body cells) – specific number of chromosomes in each species– Present as homologous pairs– E.g.: Humans: 46 chromosomes (23 homologous pairs)• Homologous chromosomes are similar– Carry genes for the same inherited characteristics (Fig. 2.4)– They are not identical– May carry different versions of the same gene• Diploid organisms have two copies of each gene (in case 1 is bad)– members of each pair don’t need to be identical– Alternative forms of the same gene: alleles• Meiosis: diploid number (2n) to the haploid number (n)– Gametes: haploid– Fusion of two gametes (fertilization) = diploid zygote• Sex-determining chromosomes are usually not homologous (Figure 2.4) yet behave as homologs in meiosis– E.g.: in humans there is an X and a Y chromosome (could be diff. in other species)VII. 2.3 Mitosis Partitions Chromosomes into Dividing Cells• Mitosis partitions chromosomes into dividing cells• Genetic material is partitioned to daughter cells during nuclear division (karyokinesis) • Cytoplasmic division (cytokinesis) follows• Cell cycle• Interphase• S phase: DNA synthesis• 2 gap phases (G1 and G2) Fig. 2.5• G0: withdraw from G1 phase, but still active (like a pit stop) • Mitosis (stages aren’t very distinct) Fig. 2.71. Prophase• centrioles divide and move apart• nuclear envelope breaks down• chromosomes condense and become visible• Sister chromatids are connected at the centromere2. Prometaphase• chromosomes move to the equatorial plane of the cell 3. Metaphase• centromeres (chromosomes) align at equatorial plane• Spindle fibers bind to kinetochores (proteins at centromere) to move chromosomes4. Anaphase• Sister chromatids (daughter chromosomes) separate from each other and migrate to opposite poles 5. Telophase • Cytokinesis (cytoplasmic division)• Uncoiling of chromosomes• Reformation of nuclear envelope• Daughter cells have full diploid compliment of chromosomesVIII. 2.4 Meiosis Reduces Chromosome # from Diploid to Haploid in Germ Cells and Spores• Reduces chromosomes by half (1 member of each homologous pair of chromosomes)– Most of the time, 1 gene is enough to get you through– Purpose: reduce by half (along with crossover) increases genetic diversity• Meiosis Overview (Fig. 2.9)– Meiosis I: reductional division– Meiosis II: equational division (still reduce # of DNA, just not reducing centromeres– No prometaphase, but all other stages present in both Meiosis I and II– S1 phase occurs before meiosis I, but not before meiosis II • Meiosis Stages– Prophase I • 5 substages (Figure 2.10):• Leptonema• Chromosomes are long single threads• Zygonema• Homologous chromosomes pair with each other (synapsis)• During synapsis, genetic material exchanges (cross over)• Endonuclease


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UNT BIOL 3451 - Introduction to Genetics/ Meiosis and Mitosis

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