BIOL 240 1st Edition Lecture 12Outline of Last Lecture I. Cellular Organization of the Genetic Materiala. Genomeb. Chromosomes II. Binary Fissiona. Prokaryotic (bacteria and archae) cell divisionb. Eukaryotic cell division and cell cyclei. The cell cycle consists of1. Mitotic phase2. Interphaseii. M phase1. Mitosisa. Prophaseb. Metaphasec. Anaphased. Telophase2. Cytokinesisiii. Three types of microtubules1. Aster2. Kinetochore3. NonkinetochoreIII. Categories of cellsa. Lack ability to divideb. Can be induced to divide when stimulatedc. High level of divisionIV. Checkpoints of the Cell Cyclea. G1b. G2c. MV. Regulatory factorsa. Cdc2 kinaseVI. External Regulationa. Density-dependent inhibitionb. Anchorage dependenceVII. Genetic changes (cancer)Outline of Current Lecture 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.I. Inheritance of Genesi. Heredityii. Asexual reproductioniii. Sexual reproductionII. Sets of Chromosomes in Human CellsIII. GametesIV. Meiosisi. Two cell divisionsii. Four haploid daughter cellsiii. Interphaseiv. Meiosis v. Meiosis IIV. Meiosis Ii. Prophase Iii. Metaphase Iiii. Anaphase Iiv. Telophase I and CytokinesisVI. Meiosis IIi. Prophase IIii. Metaphase IIiii. Anaphase IIiv. Telophase II and CytokinesisVII. MeiosisVIII. Meiosis vs. Mitosisi. 3 events unique to Meiosis (Meiosis I)i. Synapsis and crossing over in Prophase Iii. Homologous pairs at the metaphase plateiii. Separation of homologous pairs during Anaphase 1IX. Origins of Genetic Variationi. 3 mechanisms contribute to genetic variationi. Crossing overii. Independent assortment of chromosomesiii. Random fertilizationX. Evolutionary SignificanceCurrent LectureI. Inheritance of Genesa. Heredityb. Asexual reproductioni. Single individual  2 identical offspringii. Mitosisc. Sexual reproductioni. 2 parents combine genetic material to make one unique offspringii. Gametes (meiosis)II. Sets of Chromosomes in Human Cellsa. Autosomes (22)b. Sex chromosomesc. Diploid (2n) vs. Haploid (n)d. Homologous chromosomes (same genes)III. Gametesa. Gametes have half the number of chromosomes (23)b. The only human cell produced by meiosis rather than mitosisi. One set of chromosomes in each gamete1. Ovary + Testis  Meiosis  Haploids (sperm (n) and egg (n))  Fertilization  Diploids/Zygote (2n)  Mitosis and DevelopmentIV. Meiosisa. Two cell divisionsi. Meiosis I (92  46 chromosomes)ii. Meiosis II (46 23 chromosomes)b. Four haploid daughter cellsi. Meiosis I (1  2 cells)ii. Meiosis II (2  4 cells)c. Interphasei. Cell growing, DNA replication  2 sister chromatidsd. Meiosis I: separates homologous chromosomese. Meiosis II: separates sister chromatidsV. Meiosis Ia. Prophase Ii. 90% of the time in Meiosisii. Chromosomes begin to condenseiii. Homologous chromosomes pair upiv. Crossing Over1. Occurs only in meiosis, not mitosis2. During Prophase 1, as homologous chromosomes pair up3. Homologous portions of two non-sister chromatids trade placesb. Metaphase Ii. Tetrads line up at the metaphase plateii. Kinetochore microtubulesc. Anaphase Ii. Homologous chromosomes separateii. Sister chromatids remain attachedd. Telophase I and Cytokinesisi. Two sister chromatids at polesVI. Meiosis IIa. Prophase IIi. Spindle formsii. Sister chromatids move toward metaphase plateb. Metaphase IIi. Sister chromatids at metaphase plateii. Two sister chromatids are no longer genetically identical (crossing over)c. Anaphase IIi. Sister chromatids separateii. Move toward opposite polesd. Telophase II and Cytokinesisi. Chromosomes arrive at opposite polesii. Nuclei formiii. Chromosomes de-condenseVII. Meiosisa. 4 daughter cellsb. Haploid number of chromosomes = 23c. Each daughter cell is genetically distinct from others and from the parent cellVIII. Meiosis vs. Mitosisa. 3 events unique to Meiosis (Meiosis I)i. Synapsis and crossing over in Prophase I: Homologous chromosomes physically connect and exchange genetic informationii. Homologous pairs at the metaphase plate: Homologous pairs of chromosomes are positioned there in metaphase Iiii. Separation of homologous pairs during Anaphase 1IX. Origins of Genetic Variationa. 3 mechanisms contribute to genetic variationi. Crossing overii. Independent assortment of chromosomes1. Homologous chromosomes orient randomly at Metaphase I2. Each pair of chromosomes sorts material and paternal homologs into daughter cells independently of the other pairs3. For humans (n = 23), there are more than 8 million possible combinations of chromosomesiii. Random fertilization1. Any sperm can fuse with any unfertilized egg2. The fusion of the gametes (each with 8.4 million possible chromosome combinations from independent assortments) produces a zygote with approximately 70 trillion diploid combinationsX. Evolutionary Significancea. Asexual reproduction is less expensive (less ATP)b. But sexual reproduction is more universalc. Genetic variation is so important to