Lecture 1 BIO 311D 2nd EditionOutline of Current LectureI. Review of levels of organization in biologyII. ChromosomesIII. Cell division and life cyclesIV. Significance of meiosisCurrent LectureI. Review of levels of organization in biologyA. BIO 311D explores all levels of organization, emphasizes theorganism level.B. Example of exploring different levels: Hemoglobin- Structure: function relationship protein, cell, respiratorysystem- 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 thecell divides. A single replicated chromosome (consisting of twosister chromatids) just before mitosis begins contains two double-stranded DNA molecule from onlyone 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 MeiosisA. Humans have a sexual life cycle. B. Somatic cells are diploid (2n) and sperm/egg cells arehaploid (n). C. Meiosis is a necessary step in a sexual life cycle, becauseit plays the crucial reduction step. Our chromosomeswould continue to increase without meiosis. D. Mitosis haploid cells do not occur in humans, but canoccur 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 soleparent and passes copies of all its genes to its offspringwithout 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 MeiosisA. Meiosis is reduction divisionB. The products of meiosis: 4 daughter cellsC. 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 otherE. Meiosis II: Twin chromatids separate from each
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