Mar. 15, 1924 
Measurement of Linkage Values 
889 
Table I .—Measures of linkage in a back-cross 
(1) No linkage, i. e., p =. 5 
Zygotic classes. 
Observed value of p. 
AB. 
Ab. 
aB. 
ab. 
Total. 
Ab+aB 
n 
Q. 
Perfect population. 
1 
1 
I 
I 
4 
0. 5000 
0. 5000 
25 per cent a gametes not effec¬ 
tive . 
4 
4 
3 
3 
14 
. 5000 
. 5000 
2 5 per cent a and b gametes not 
effective. 
16 
12 
12 
9 
49 
.4898 
. 5000 
25 per cent a and B gametes not 
effective. 
12 
16 
9 
12 
49 
. 5102 
. 5000 
25 per cent a zygotes wrongly 
classified as A . 
5 
5 
3 
3 
16 
. SOOO 
. 5000 
(2) Dominants linked, 25 per cent crossingover, i. e. f p =.25 
Perfect population. 
3 
1 
1 
3 
8 
0. 2500 
0. 2500 
2 5 per cent a gametes not effec¬ 
tive. 
12 
4 
3 
9 
28 
. 2500 
. 2500 
25 per cent a and b gametes not 
effective. 
16 
4 
4 
9 
33 
. 2424 
.2500 
25 per cent a and B gametes not 
effective. 
25 per cent a zygotes wrongly 
36 
9 
16 
3 6 
97 
•2577 
. 2500 
classified as A. 
13 
7 
3 
9 
32 
•3125 
. 2976 
Table II .—Comparison of methods of measuring linkage in F 2 
No linkage, i. e., p —.5 
Zygotic classes. 
Observed value of p. 
AB. 
Ab. 
aB. 
ab. 
Total. 
Q- 
P. 
T. 
Perfect population. 
25 per cent a gametes 
9 
3 
3 
I 
16 
0. 5000 
0. 5000 
0. 5000 
not effective. 
2 5 per cent a and b gam¬ 
120 
40 
27 
9 
196 
. 5000 
• 5 6 24 
. 5000 
etes not effective. 
2 5 per cent a and B gam¬ 
1,600 
360 
360 
81 
2, 401 
. 5000 
•6336 
. 5260 
etes not effective. 
1, 320 
640 
297 
144 
2,401 
. 5000 
.4685 
.4798 
25 per cent a zygotes die. 
25 per cent a and b 
12 
4 
3 
1 
20 
. 5000 
•5477 
. 5000 
zygotes die. 
25 per cent a and B 
144 
36 
36 
9 
225 
. 5000 
. 6000 
•5133 
zygotes die. 
25 per cent a zygotes 
108 
48 
27 
12 
195 
. 5000 
. 4804 
. 4886 
called A . 
Double recessive class 
39 
13 
9 
3 
64 
. 5000 
• 5590 
. 5000 
not recovered. 
9 
3 
3 
0 
IS 
. 0000 
.4472 
. 0000 
