BIOL1006 Lecture Notes - Lecture 10: Chromosome, Barr Body, Lucilia Cuprina
31 Jul 2018
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More than one gene, more than one character l10 (13/04: dihybrid cross. Backcrosses and test crosses: backcross: mate f1 to putative recessive parent, test cross: mate unknown to known recessive, expected ratio is 1:1:1:1. Incomplete dominance: 1:2:1 in f2 generation (red + white flower gives red, pink, or white) Barr bodies: random inactivation of an x chromosome in women, x inactivation in cats. Quantitative characters: continuous variation eg. height, arctic foxes - genes controlling the colour white fur get shut down during the summer, epistasis: the suppression of the effect of one gene by another. Mapping the genome l11 (16/04: ab and ab gametes can only arise from recombination (rarer as it requires a recombination event) Wwcrcr wwcrcr wwcrcr: map distance = ((number of recombinants)/total number of progeny) x 100. B-------9. 0--------cn----------9. 5---------vg (18. 5 total: double crossover underestimates the recombination fraction due to double recombinants.
