Unformatted text preview: tances
a+
a+
a+
a+
a
a
a
a b+ c DCO
b+ c+ P
b c+ SCO
b c SCO
b+ c+ SCO
bc P
b+ c SCO
b c+ DCO 9 pick any 2 genes to start with e.g., a and b
1654 sum all the offspring with recombinant
131 phenotype of a+ b or a b+ (ignore c)
252 =131 + 252 + 241 + 118 = 742
241
1779 divide by total number of offspring and
118 multiply by 100
13 = 742 x 100 = 17.7 m.u. a
b
4197 4197
repeat for each gene pair
a and c = 9+252+241+13/4197*100 = 12.3
b and c = 9+131+118+13/ 4197 *100 = 6.4 12 Construct the map
= 17.7 m.u. a
= 12.3 m.u. a
= 6.4 m.u. b b
c
c a c
12.3 b
6.4 17.7 BUT…..
12.3 + 6.4 = 18.7 m.u. not 17.7 as observed
WHY? due to double cross overs.
13 Correction for distances between a and b
calculation of m.u. between a and b does not take
into consideration double crossovers
does not reflect all of the recombination events that
produce a b+ or a+ b a c a+ c+ b+ c+ a
a+ b + b c b+ 14 Correction for distances between a and b
a
c+
b
a+ + c b+ look like parentals for a and b, but are not
these were not included in original calculation
go back to original calculation for a and b
and include these numbers
15 Finding map distances
a+
a+
a+
a+
a
a
a
a b+ c DCO
b+ c+ P
b c+ SCO
b c SCO
b+ c+ SCO
bc P
b+ c SCO
b c+ DCO 9 pick any 2 genes to start with e.g., a and b
1654 sum all the offspring with recom...
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This document was uploaded on 02/25/2014.
 Winter '14
 Genetics

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