Re: HYB: duh - probabilities

Linda, just remember that four things taken two at a time, order not
significant, gives six, not four, possibilities.  1 and 2, 1 and 3, 1 and 4,
2 and 3, 2 and 4, 3 and 4.  That makes six combinations.  Six times six is
thirty-six.  A Punnett square of tetraploid pairing, all pairing random
gives the simple ratios in a 36-cell box.

Too bad it isn't that simple.

What TWOI is talking about is that the pairing of chromosomes out of the
four in a set is NOT always random.  It may be selective, or worse, form
trivalent or quadrivalent (three in the marriage, four in the marriage)
kinds of pairing, or worse yet, part of a chromosome pairs with a, the other
part with b, but b also pairs with c at the other end---you get a daisy
chain.  Ouch!  That really throws the ratios into a kettle to stir.

Also, the probabilities of some aspects of genetics varies with the distance
of a DNA sequence from the centromere (oh headache!), that wasp-waist
pinched part of a chromosome where the microfiliments latch on in drawing
chromosomes into their array at meiosis and mitosis.  That can mess up the
simplicity of ratios too.

Oy Weh!  Why can't some things in life be simple, hunh?

Neil Mogensen  z 7  Reg 4  western NC mountains

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