Presentation on theme: "Meiosis Organisms that reproduce sexually have specialized cells called gametes (sex cells) Gametes are the result of a type of cell division called meiosis."— Presentation transcript:
1 MeiosisOrganisms that reproduce sexually have specialized cells called gametes (sex cells)Gametes are the result of a type of cell division called meiosis
2 Diploid and haploidAlmost all human cells are diploid or containing two homologous sets of chromosomes2n = 46Eggs and sperm cells (gametes) are haploid or containing a single set of chromosomesn = 23
3 ORGANISM (Genus species) NUMBER OF CHROMOSOMES Homo sapiens (human)______________________________46Mus musculus (house mouse)_________________________40Drosophila melanogaster (fruit fly)_____________________8Caenorhabditis elegans (microscopic roundworm)_________12Saccharomyces cerevisiae (budding yeast) ______________32Arabidopsis thaliana (plant in the mustard family) ________10Xenopus laevis (South African clawed frog)______________36Canis familiaris (domestic dog)________________________78Gallus gallus (chicken) ______________________________28Zea mays (corn or maize)____________________________20Muntiacus reevesi (the Chinese muntjac, a deer) _________23Muntiacus muntjac (its native american cousin) __________6Myrmecia pilosula (an ant) ___________________________2Parascaris equorum var. univalens (parasitic roundworm)___2Cambarus clarkii (a crayfish)__________________________200Equisetum arvense (field horsetail, a plant)______________216
12 haploid egg and spermdiploid zygoteIn the human life cycle a haploid egg and sperm fuse and form a diploid zygote. Mitosis produces an embryo with numerous cells that continue to multiply and develop.
14 Genetic variation is a result of two processes that occurs during meiosis: Independent assortment of chromosomes, andCrossing overNOTE: Mutations (random changes in gene sequences) are a cuse of genetic variation.
15 During metaphase I, the independent assortment of chromosomes that end up in the resulting cells occurs randomly
16 Crossing over: exchange of genetic material between homologous chromosomes during prophase I of meiosis
17 Genetic recombination: new combination of genetic information in a gamete as a result of crossing over during prophase I of meiosis
19 MITOSIS MEIOSIS TYPE OF CELL (that undergoes this division) (pages 195, 200, & 201)MITOSISMEIOSISTYPE OF CELL (that undergoes this division)# OF CELL DIVISIONSStarts/ends as diploid or haploid cell# OF DAUGHTER CELLS# OF CHROMOSOMES AFTER DIVISIONEXCHANGE OF DNA (Y/N)UNIQUE OR IDENTICAL CELL AFTER DIVISION