BIOL-L 211 Lecture 6 Outline of Last Lecture I. DNA ComponentsII. DNA Genetic SequenceIII. TransposonsIV. PseudogenesOutline of Current Lecture I. Cell DivisionII. InterphaseIII. MitosisIV. MeiosisCurrent LectureCell CycleI. Cell DivisionA. General1. DNA replicates2. DNA passed on to daughter cellsB. Types of Cell Division1. Binary fission: occurs in prokaryotes, asexual, mechanism still not fully discovered2. Mitosis: occurs in somatic cells (aka all non-gamete body cells- soma means body)3. Meiosis: occurs in gametesII. Interphase: Longest part of cell cycle; phase during which cell prepares for mitosisA. G1: Cell prepares for chromosome segregation (there are checkpoints)These 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.B. S-phase: Replication of DNA occurs1. Chromosomes de-condense which allows replication to proceed2. Sister-chromatid cohesion is established (cohesion is what holds the sister-chromatids together)3. Cohesion: ring-shaped protein complex around copied DNAC. G2: Cell prepares for cell divisionIII. Mitosis: (final product: 2 new daughter cells)A. Prophase: chromosomes condense & nuclear envelope breaks downB. Metaphase: chromosomes line up along metaphase plate1. The goal is for bivalent attachment to microtubules from BOTH poles of the cell2. If this goal is not achieved, cancer or other problems may resultC. Anaphase: cohesion digested & sister-chromatids are pulled to opposite poles1. Fun fact: Proteolysis is a really cool word for the digestion of enzymesD. Telophase: each chromosome is at a spindle pole, the nuclear envelope reforms, and DNA de-condenses againE. Cytokinesis: Separation of daughter cellsIV. Meiosis: (final product: 4 genetically different daughter cells)A. Meiosis I: (separation of homologous chromosomes)1. Interphase: DNA replication2. Prophase I: chromosomes condense; pairs of homologous chromosomes aligna. *Crossing over occurs here!!!*3. Metaphase I: Pairs of homologous chromosomes align on metaphase plate4. Anaphase I: Breakdown of cohesion at arms not at pairs such that chromosomes are still paired after this5. Telophase I & Cytokinesis: Separation of cell; each half has haploid set of replicated chromosomes (but NOT identical sister chromatids because of crossing over)B. Meiosis II: (separation of sister-chromatids)1. Prophase II: Have 2 sister chromosomes with centromere2. Metaphase II: Chromosomes align and sister chromatids attach to microtubules from both poles3. Anaphase II: Sister chromatids separate (cohesion is now GONE)4. Telophase II & Cytokinesis: Nuclei form, chromosomes de-condense, and cytokinesis
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