Sex-linked Inheritance in Drosophila

by Thomas Hunt Morgan; Calvin B. Bridges

LINKAGE OF FORKED, BAR, AND FUSED.

This value of 58 gave the furthest locus to the right obtained up to that time, since forked is slightly beyond rudimentary. Later, the locus for bar-eye was found still farther to the right, and the locus for fused even farther to the right than bar. A cross was made involving these three gens. A forked (not-bar) fused male was bred to a (not-forked) bar (not-fused) female and gave bar females and males. The F₁ females were back-crossed singly to forked fused males with the result shown in table 41.

Table 41.—P₁ bar ♀ ♀ × forked fused ♂ ♂. B. C. F₁ bar ♀ × forked fused ♂ ♂.

Reference.									Total.
	Forked fused.	Bar.	Forked bar.	Fused.	Forked.	Bar fused.	Forked bar fused.	Wild- type.
163	45	55	..	1	4	2	..	..	108
164	71	90	..	..	4	1	..	..	166
165	97	106	..	..	2	4	..	..	209
11	21	35	..	..	1	2	..	..	59
33	15	23	..	..	..	1	..	..	39
Total.	250	309	..	1	11	10	..	..	581

The same three points were combined in a different way, namely, by mating forked females to bar fused males. The bar daughters were back-crossed to forked fused males and gave the results shown in table 42.

Table 42.—P₁ forked ♀ ♀ × bar fused ♂ ♂. B.C. F₁ bar ♀ × forked fused ♂ ♂.

Reference.									Total.
	Forked.	Fused bar.	Forked bar fused.	Wild- type.	Forked fused.	Bar.	Forked bar.	Fused.
158	131	124	1	..	3	3	..	..	262
159	31	45	..	..	..	..	..	..	76
160	29	23	..	..	1	2	..	..	55
161	24	11	1	..	..	..	..	..	36
162	96	91	2	..	1	1	..	..	191
Total.	311	294	4	..	5	6	..	..	620

By combining the results of tables 41 and 42 data are obtained for cross-over values from which (by balancing the inviable classes, as explained in table 43) the element of inviability is reduced to a minimum.

Table 43.