Basic Birds & Bees
(Jan. 3, 2008) I had intended to write about ferns and their shady lives, but realized that I should first review the fundamentals of reproduction. The diagram shows the basic concepts, under the assumption that each parent provided one chromosome to form a diploid cell with a pair of chromosomes. (Further simplification is my equating cells with nuclei.)
Mitosis is the division of cells for growth. The pale and dark chromosomes each duplicate their DNA to produce two duplicated chromosomes. These are pulled apart to yield the four chromosomes needed for two new cells, each identical to the initial diploid cell.
Meiosis (my-oh-sis) is necessary for sexual reproduction and increases genetic diversity by allowing exchange of DNA between paired chromosomes. By dividing twice after just one duplication event it produces four haploid gametes (such as sperm and eggs) for immediate fertilization, or spores which can grow before eventually producing gametes. Fertilization occurs when two haploid gametes fuse to yield one diploid cell.
Variations on this scheme are endless: Certain female ants have one pair of chromosomes, as in the diagram, but males grow from unfertilized eggs and are thus haploid. One species of fern has 630 pairs of chromosomes*. Choreographing their meiosis keeps God entertained. A woman has two meters of DNA coiled into 23 pairs of chromosomes. The DNA contained in her 10 trillion cells could encircle the Earth 500,000 times. That’s enough to boggle any man’s mind.
*S.J.Gould inBully for Brontosaurus, W.W.Norton & Co. NY 1991.
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Today
Winter Classic Table Tennis Tournament
sports / 11:30 a.m. Arcata Community Center, 321 Community Parkway. Compete in 12 and under, beginners, intermediate, advanced or seniors groupings. Prizes for winners. $10/$5 kids 12 and under. 601-5447.
Audubon Society Field Trip
outdoors / 9 a.m. Humboldt Bay National Wildlife Refuge, 1020 Ranch Road, Loleta. Meet at Refuge Visitor Center off Hookton Road. Leisurely, two- to three-hour trip intended for people wanting to learn birds of Humboldt Bay area. 822-3613.
Open Celtic Music Session
music / 3 p.m. Cafe Veritas/Mosgo's, 180 Westwood Center, Arcata. Informal monthly gathering of musicians playing Irish and other Celtic music. Hosted by Seabury Gould. seaburygould.com. 845-8167.
Nonviolence Action Camp
etc. / 10 a.m. Chinmaya Mission near Piercy. Weekend-long direct action orientation features workshops, role playing, seminars, ceremonies and field trips. Bring food, bedding, warm clothes, signs, banners, bikes, drums, acoustic instruments. Pre-register. saverichardsongrove.org. 932-5898.
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