Lecture 1 BIO 311D 2nd Edition Outline of Current Lecture I II III IV Review of levels of organization in biology Chromosomes Cell division and life cycles Significance of meiosis Current Lecture I Review of levels of organization in biology A BIO 311D explores all levels of organization emphasizes the organism level B Example of exploring different levels Hemoglobin Structure function relationship protein cell respiratory system Quantitative skills Mechanisms of evolution Phylogenetic analysis II Chromosomes A Each cell in your body except for gametes sperm or eggs contains 46 chromosomes each of which replicates before the cell divides A single replicated chromosome consisting of two sister chromatids just before mitosis begins contains two double stranded DNA molecule from only one of your parents B A pair of homologous chromosomes has the same gene loci and loci position but the allele presented at the loci may differ C One homologous pair contains DNA from one of your parents in one chromosome and DNA from the other parent in the other chromosome III Cell Division Life Cycles and Significance of Meiosis A Humans have a sexual life cycle B Somatic cells are diploid 2n and sperm egg cells are haploid n C Meiosis is a necessary step in a sexual life cycle because it plays the crucial reduction step Our chromosomes would continue to increase without meiosis D Mitosis haploid cells do not occur in humans but can occur in other organisms E In plants sperm and egg nuclei are produced by mitosis by a tiny multicellular haploid plant body F Asexual reproduction a single individual is the sole parent and passes copies of all its genes to its offspring without the fusion of gametes Through mitotic cell division DNA is copied and allocated equally to two daughter cells The genomes of the offspring are exact copies of the parent s genome Examples Diploid organism hydra Haploid organism bread mold G Sexual reproduction two parents give rise to offspring that have unique combinations of genes inherited from the two parents Offspring of sexual reproduction vary genetically from their siblings and both parents Meiosis occurs Examples Diploid organism birds Diploid w self fertilization tapeworm IV Significance of Meiosis A Meiosis is reduction division B The products of meiosis 4 daughter cells C If a cell with 24 pairs of chromosomes undergoes meiosis there will result four daughter cells and within each daughter cell there are 24 chromosomes D Meiosis I Chromosomes condense Tetrads form Homologs separate from each other E Meiosis II Twin chromatids separate from each other
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