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Mysterious Meiosis Chapter 13 Notes I. Asexual Reproduction A. B. Examples..... Binary Fision,…. Splitting in two Budding…”chip off the old block” - hydra Cloning… genetically indentical individuals II. Sexual Reproduction A. B. Examples... Most multicellular organisms (including plants) III. Very Important Vibrant Vocabulary Heredity: Transmission of ____________ from one generation to the next Variation: Offspring differ from their _______________ and _______ Genetics: Scientific study of heredity and hereditary variation Locus: A gene’s specific location along the length of a chromosome *Genes program cells to make proteins, proteins produce traits* Karyotype: Organization of a cell’s chromosomes by number, size and type Diploid: A cell with a _________ set of chromosomes (23 pairs = 46 chromosomes) Homologous Pairs: A pair of chromosomes that have the same ___________, but may have different forms of the genes (1 from _____ and one from __________) Sex Chromosomes: A special pair of chromosomes that make us girl or boy XXXYAutosomes: The 22 other pairs of chromosomes Tetrad: Homologous chromosomes that are copied and stuck at the centromere (Four copies of the chromosome, Two from each parent) Haploid (gametes): Cells with ________ the chromosomes, No homologous pairs 22 autosomes + 1 sex chromosome = 23 chromosomes Zygote: IV. Meiosis...The Details **Diploid to Haploid ** 1. Interphase I ** 2. Prophase I ** **Synapsis… ** **Spindle fibers form, nuclear membrane disappears 3. Metaphase I ** 4. Anaphase I ** ** 5. Telophase I and Cytokinesis ** 6. Prophase II ** 7. Metaphase II * 8. Anaphase II *Centromeres break and sister chromatids (chromosomes) move to the poles 9. Telophase II and Cytokinesis: *Chromosomes to chromatin *Four daughter cells are formed **Ta Da !! Sex cells !! V. Sources of Variation in Meiosis A. __________________________________________ When chromosomes line up during Metaphase I, they do so independently of each other. This results in different combinations of chromosomes in gametes because every time they line up they do it differently. B. __________________________________ During Prophase I, homologous chromosomes pair tightly and pieces of one chromosome can cross over to the homologous chromosome. This results in chromosomes that have a combination of maternal and paternal genes. C. __________________________________ The egg that is fertilized is one of 8 million chromosome combos. The sperm that reaches the egg is also one of 8 million combos. This results in over 64 trillion combos of sperm and egg from one set of parents (this is without crossovers). Be sure to look over page 261, Figure 13.10!!! Very possible essay!!!! VI. Gametogenesis in Humans (pg. 1021) A. Oogenesis *Production of ova, mature eggs *Occurs in the _________________. *____________________: Stem cells that make eggs *These stem cells multiply and then begin __________. They stop meiosis at _________________. The cells at this stage are called ___________________________. The cells remain here as follicles until puberty. *___________________________ stimulates a follicle to grow and complete ______________ and to start _______________. *Meiosis II stops....now the cell is called a ____________________. *Ovulation occurs, the cell then finishes Meiosis II when it is __________________________________. B. Spermatogenesis *Production of mature sperm *Occurs in the ____________ __________ of the testes. *____________________: Stem cells that make sperm *______________ million sperm per ejaculation. Men can ejaculate daily with no loss of fertility capacity. C. The difference between Spermatogenesis and Oogenesis 1. In oogenesis meiotic divisions are ______________ (cytokinesis). *One egg cell is created, three small polar bodies degenerate In spermatogenesis meiotic divisions are ____________. *Four sperm are created from each spermatogonia 2. At birth, the ovary contains all of the _____________ it will ever have. Spermatogonia go through _______________ all through a man’s life. 3. Oogenesis has long “resting” periods. Spermatogenesis is uninterrupted.