BIO 1201 1nd Edition Lecture 13 Outline of Last Lecture I.Cell cycle exitsII.CloningIII.CancerIV.How to not get cancerOutline of Current Lecture V.Sexual ReproductionVI.MeiosisVII.Why aren’t siblings identical?Current LectureI. Sexual Reproduction: combination of genetic material from two individualsa. Before sex, the cells involved (sperm and eggs—gametes) must undergo a specialcell division that cuts the genetic material in halfb. Humans have two sets of chromosomes (or genomes); one set comes from each parentc. Specialized cell division required fro sex is called meiosisi. Meiosis is a cell division that halves the ploidy of a cellII. Meiosis: essential for sexual reproduction (otherwise every generation would have twice the DNA/ploidy)a. Only occurs in specialized cells called germ cellsb. Occurs by a series of two cell divisions called meiosis 1 and meiosis 2i. A germ cell basically goes through interphase (copies DNA), then:1. Meiosis 1: homologous chromosomes divide2. Meiosis 2: chromatids dividec. In humansi. Males: meiosis produces 4 cells, all of which become spermThese 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.ii. Females: meiosis produces 4 cells, one of which becomes ova (egg) and the other three become polar bodies that ultimately degradeIII. Why aren’t siblings identical?a. Because meiosis and sex generate genetic diversity in three waysi. Random mutation during DNA replication (60-70 per generation)ii. Random assorting of chromosomes during meiosis 11. Number of possibilities is 2^23, which equals 8,338,608iii. Crossing Over (Meiosis 1): homologous chromosomes can occasionally exchange pieces of DNA using
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