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Meiosis
Biology ch 12
Term | Definition |
---|---|
asexual reproduction | involves one parent and produces a clone |
sexual reproduction | involves two parents |
examples of asexual reproduction | binary fission, budding, fragmentation, |
Karyotype | used to identify sex or aneuploidy (abnormal number of chromosomes) |
chrosomes 1-22 | autosomes |
chrosome 23 | sex chrosomes |
homologous chrosomes | similar in sturcture and carry the same types of genes, one from each parent |
diploid | contain a full set of chrosomes form both parents |
stomatic cells | all body cells: skin, nerve |
haploid | cells that contain 1/2 the full set of chrosomes |
gametes | reproductive cells; egg and sperm |
how many divisions occur in meiosis | 2 |
in what cells does meiosis occur in | sex cells |
how many chromosomes end up in the daughters cells | half the amount |
how many daughter cells result in meiosis | 4 |
Spermatogenesis | results in 4 equal sperm cells |
oogenesis | resluts in 1 large egg and 3 polar bodies |
interphase | longest phase, contians G1, S, G2 |
Prophase 1 | snapsis occurs, crosing over occurs, spindle fibers form. chrosomes condense |
synapsis | homologous chrosomes come together to form a tetrad |
tetrad | two chrosomes or for chromatids |
crossing over | segments of nonsister chromatids break and reattach to the other chromatid, causes genetic recombiantion |
chiasmata | where chrosomes touch each other and exchange genes |
metaphase 1 | shortest phase, tetrads align, indepnednet assortment occurs |
anaphase 1 | homologous chrosomes seperate and move towards the poles, sister chromatids remaind attached at their centromeres |
telophase 1 | each pole now has haploid set of chrosomes, cytokinesis occurs and two haploid daughter cells are formed |
interkinesis | short period of time between meiosis 1 and 2 |
prophase 2 | nucleus and nucleolus dissapear, chrosomes condense, spindle forms |
metaphase 2 | chrosomes line up at equator |
anaphase 2 | sister chromatids seperate |
telophase 2 | nuclei and nucleoli reform, spindle disappears, cytokinesis occurs, 4 haploid daughter cells are produced |
independent assortment | chrosomes assort independently from one another during meiosis |
random fertilization | whichever gamete is involved in actual fertilization determines the genes of the offspring |
nondisjunction | occur when homologous chrosomes fail to seperate at meiosis 1 or when chromatids fail to separate at meiosis 2 |