Meiosis Organisms that reproduce sexually have specialized cells called gametes (sex cells) Gametes are the result of a type of cell division called meiosis.

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Presentation transcript:

Meiosis Organisms that reproduce sexually have specialized cells called gametes (sex cells) Gametes are the result of a type of cell division called meiosis

Diploid and haploid Almost all human cells are diploid or containing two homologous sets of chromosomes 2n = 46 Eggs and sperm cells (gametes) are haploid or containing a single set of chromosomes n = 23

ORGANISM (Genus species) NUMBER OF CHROMOSOMES Homo sapiens (human)______________________________46 Mus musculus (house mouse)_________________________40 Drosophila melanogaster (fruit fly)_____________________8 Caenorhabditis elegans (microscopic roundworm)_________12 Saccharomyces cerevisiae (budding yeast) ______________32 Arabidopsis thaliana (plant in the mustard family) ________10 Xenopus laevis (South African clawed frog)______________36 Canis familiaris (domestic dog)________________________78 Gallus gallus (chicken) ______________________________28 Zea mays (corn or maize)____________________________20 Muntiacus reevesi (the Chinese muntjac, a deer) _________23 Muntiacus muntjac (its native american cousin) __________6 Myrmecia pilosula (an ant) ___________________________2 Parascaris equorum var. univalens (parasitic roundworm)___2 Cambarus clarkii (a crayfish)__________________________200 Equisetum arvense (field horsetail, a plant)______________216

Horsetail

HUMAN KARYOTYPE A display of all the 46 chromosomes of an Individual.

9.5 page 2

Remember Mitosis?

MITOSIS

Meiosis

haploid egg and sperm diploid zygote In 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.

2 diploid daughter cells http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120074/bio17.swf::Comparison%20of%20Meiosis%20and%20Mitosis MEIOSIS MITOSIS Original diploid cell 2n 2n 2n 2 diploid daughter cells

Genetic variation is a result of two processes that occurs during meiosis: Independent assortment of chromosomes, and Crossing over NOTE: Mutations (random changes in gene sequences) are a cuse of genetic variation.

During metaphase I, the independent assortment of chromosomes that end up in the resulting cells occurs randomly

Crossing over: exchange of genetic material between homologous chromosomes during prophase I of meiosis

Genetic recombination: new combination of genetic information in a gamete as a result of crossing over during prophase I of meiosis

MITOSIS MEIOSIS TYPE OF CELL (that undergoes this division) (pages 195, 200, & 201) MITOSIS MEIOSIS TYPE OF CELL (that undergoes this division) # OF CELL DIVISIONS Starts/ends as diploid or haploid cell # OF DAUGHTER CELLS # OF CHROMOSOMES AFTER DIVISION EXCHANGE OF DNA (Y/N) UNIQUE OR IDENTICAL CELL AFTER DIVISION

Development of egg and sperm http://www.sparknotes.com/testprep/books/sat2/biology/chapter7section2.rhtml