04BIS10110152013RecombinLect4

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Unformatted text preview: alled the “mapping However, function” can be used to correct for the effects of multiple crossovers and provide more accurate map distances. more e-m mi ƒ(i) = i! or RF = 1/2(1- e-m ) RF A B C a b c BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez 44 Mapping Function: Solving for m Mapping ­ By solving for e-m (the natural log of the mean crossovers per meiosis) you can find m, using a using calculator or natural log table (see next slide). calculator RF = 1/2(1- e-m ) RF e-m = 1 - RF(2) m/2 = RF m/2 RF ­ Since it has been shown empirically that m/2=RF, Since you can easily convert the original RF values into accurate map distances. For examples, if RF = 27.5% or 27.5 m.u. then... 27.5% e-m = 1 - 0.275(2) m = 0.8 0.8 e-m = 1 - 0.55 e-m = 0.45 0.8/2 = 0.4 or 40 m.u. 0.8/2 0.4 BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez 45 Mapping Function Values of e-m for m Values from 0 to 1* Values m 0.000 0.050 0.100 0.150 0.200 0.250 0.300 0.350 0.400 0.450 0.500 e-m 1.00000 0.95123 0.90484 0.86071 0.81873 0.77880 0.74082 0.70469 0.67032 0.63763 0.60653 m 0.550 0.600 0.650 0.700 0.750 0.800 0.850 0.900 0.950 1.000 e-m 0.57695 0.54881 0.52205 0.49659 0.47237 0.44933 0.42741 0.40657 0.38674 0.36788 If e-m = 0.45, then m = 0.80. If m/2 = RF, then an RF equals 0.4 or 40 m.u., not 27.5 m.u. not *Values for m greater than 1 can be obtained from an electronic calculator or by using logarithms. Source: F. James Rohlf and Robert R. Sokal, Statistical Values Source: Tables, 3d ed. W. H. Freeman and Company, 1995. Tables, BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez 46 Mapping Function shows that RF is half the mean crossovers. unadjusted adjusted RF = m/2 = 0.4 RF 40 80 BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez 47 Chi-square test f...
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