Presentation on theme: "Aim: How is chromosome number maintained in the species from generation to generation? Group Work: How many chromosomes are found in human cells? How many."— Presentation transcript:
Aim: How is chromosome number maintained in the species from generation to generation? Group Work: How many chromosomes are found in human cells? How many chromosomes pass from each parent to the child?
Oogenesis Egg formation takes place in the ovaries Egg contains the n number of chromosomes
Spermatogenesis Spermatogenesis — takes place in the testes. Each sperm cell contains the n number of chromosomes
Comparison of (Meiosis) Spermatogenesis Oogenesis 1. production of sperm cell from puberty to the death of the male 2. produce 4 haploid sperm cells 3.very small cells with a tail 1. viable eggs are produced from puberty to menopause 2. produce 1 haploid egg cell and three smaller polar bodies 3. large cells
Diploid numbers of some commonly studied organisms (as well as a few extreme examples) Homo sapiens (human)46 Mus musculus (house mouse)40 Drosophila melanogasterDrosophila melanogaster (fruit fly)8 Caenorhabditis elegansCaenorhabditis elegans (microscopic roundworm)12 Saccharomyces cerevisiaeSaccharomyces cerevisiae (budding yeast)32 Arabidopsis thalianaArabidopsis thaliana (plant in the mustard family)10 Xenopus laevis (South African clawed frog)36 Canis familiaris (domestic dog)78 Gallus gallus (chicken)78 Zea mays (corn or maize)20 Muntiacus reevesi (the Chinese muntjac, a deer)23 Muntiacus muntjac (its Indian cousin)6 Myrmecia pilosula (an ant)2 Parascaris equorum var. univalens (parasitic roundworm) roundworm 2 Cambarus clarkii (a crayfish)200 Equisetum arvense (field horsetail, a plant)horsetail216
Human Homologous Chromosomes
Fertilization… restores the diploid number of chromosomes to the egg cell making it a zygote n + n = 2n