2. Gregor Mendel 1822 Austrian monk University of Vienna In charge of the Garden
3. What Gregor Mendel Knew… Each organism must inherit a single copy of every gene from each of its “parents” Each of the organisms gametes must contain just one set genes When gametes are formed, there must be a process that separates the 2 sets of genes so each gamete gets one set
9. Chromosome Number Homologous chromosomes Chromosome that has a corresponding chromosome from the opposite-sex parent Fruit fly has 8 chromosomes 4 from mom 4 from dad
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11. Diploid Di= two sets Cell that contains both sets of homologus chromosomes Cell contains 2 complete sets of chromosome 2 complete sets of genes Number of chrms in diploid cell represented by 2N For Drosophilia (fruit fly) 2N=8 Mendel said: Each adult cell contains two copies of each gene
12. Haploid Means “one set” Refers to cells that contain only one set of chromosomes Gametes (sex cells) Represented by N Drosophilia fruit fly N=4
14. Meiosis Process of reduction division in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell
15. Meiosis 2 distinct stages Meiosis I A diploid cell enters here Meiosis II At the end of this, the diploid cell that entered meiosis has become 4 haploid cells
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18. Meiosis I Before meiosis 1, each chromosome is replicate Then they divide like in mitosis What happened in mitosis? PMAT Tetrad STRUCTURE MADE WHEN EACH CHROMOSOME PAIRS UP WITH ITS HOMOLOGOUS CHROMOSOME 4 CHROMATIDS IN A TETRAD
19. Prophase 1 Each chromosome pairs with its homologous chromosome making a tetrad As they pair up in tetrads, chromosomes exchange portions of their chromatids in the process …. CROSSING OVER
23. Now what do we have? 2 new daughter cells Are they identical to the parents? No Let’s say the parent started with 8 chromosomes Each daughter cell has 8 chromosomes but they are different because of crossing-over Each daughter cell has a set of chromosomes and alleles different from each other and different from the parent diploid cell
24. Meiosis II Unlike Mitosis, Neither cell goes through a round of chromosome replication
25. Prophase II Meiosis I resulted in 2 “seemingly” diploid cells Remember they are genetically different b/c of crossing over in prophase I We still need to cut this number in half to reach our goal of 4 haploid cells
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29. Gamete Formation Male Haploid gametes produced by meiosis are called sperm Female Haploid gamete produced by meiosis is called an egg Cell divisions at the end of meiosis one and two are uneven so one cell gets most of the cytoplasm (the EGG) and the other three are called polar bodies (don’t participate in reproduction)
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35. Mitosis vs. Meiosis Mitosis Results in the production of two genetically identical DIPLOID cells Daughter cells have sets of chromosomes identical to each other and to parent cell MITOSIS allows body to grow and replace other cells Asexual reproduction Meiosis Results in four genetically different HAPLOID cells MEIOSIS is how sexually reproducing organisms make gametes
