Sex-linked Inheritance in Drosophila

by Thomas Hunt Morgan; Calvin B. Bridges

LINKAGE OF DEPRESSED AND BAR.

Depressed (not-bar) males mated to (not-depressed) bar females gave bar daughters. Two of these were back-crossed singly to depressed males and gave the results shown in table 49. Males and females were not separated, since they should give the same result.

Table 49.—P₁ depressed ♀ ♀ × bar ♀ ♀. B.C. F₁ bar ♀ × depressed ♂ ♂.

Reference.	Non-cross-overs.		Cross-overs.		Total.	Cross- over values.
	Depressed.	Bar.	Depressed bar.	Wild- type.
66 I	48	51	21	41	161	39
67 I	85	104	44	70	303	38
Total.	133	155	65	111	464	38

LINKAGE OF CHERRY, DEPRESSED, AND VERMILION.

The linkage value 38 (see table 49) indicates that depressed is somewhere near the opposite end of the series of sex-linked factors from bar. The locus could be more accurately determined by finding the linkage relations of depressed with gens at its end of the chromosome. Accordingly, depressed females were crossed to cherry vermilion males. F₁ gave wild-type females and depressed males. The daughters bred again to cherry vermilion males gave the results shown in table 50. The data only suffice to show that the locus of depressed is about midway between cherry and vermilion, or at about 15 units from yellow.

The F₁ males in the last experiment did not have their wings as much depressed as is the condition in stock males, and in F₂ most of the depressed winged males were of the F₁ type, although a few were like those of stock. This result suggests that the stock is a double recessive, i. e., one that contains, in addition to the sex-linked depressed, an autosomal factor that intensifies the effect of the primary sex-linked factor.

Table 50.—P₁ depressed ♀ × cherry vermilion ♂ ♂.