Part 11
In order to determine the location of facet in the first chromosome, one of the facet males which appeared in culture 66 was crossed out to vermilion sable females. Three of the wild-type daughters were back-crossed to vermilion sable males. The females of the next generation should give data upon the linkage of vermilion and sable, while the males should show the linkage of all three gens, facet, vermilion, and sable. The offspring of these three females are cla.s.sified in table 59.
The cross-over fraction for vermilion sable as calculated from the females is 19/194. The cross-over value corresponding to this fraction is 10 units, which was the value found in the more extensive experiments given in the section on sable.
It will be noticed that the results in the males of culture 150 are markedly different from those of the other two pairs. While the sable males are fully represented, their opposite cla.s.ses, the gray males, are {77} entirely absent. This result is due to a lethal factor, lethal 5, which appeared in this culture for the first time.
The males of the two cultures 149 and 151 give the order of gens as facet, vermilion, sable; that is, facet lies to the left of vermilion and toward yellow. The cross-over values are: facet vermilion 40; vermilion sable 12; facet sable 42. Since yellow and vermilion usually give but 34 per cent of crossing-over, this large value of 40 for facet vermilion shows that facet must lie very near to yellow.
TABLE 59.--_P_1 facet_ [male] _vermilion sable_ [female] [female]. _B.C.
F_1 wild-type_ [female] _vermilion sable_ [male] [male].
+----------+----------------------------------+
F_2 females.
+----------------+-----------------+
Non-cross-overs.
Cross-overs.
Reference.+---------+------+----------+------+
Vermilion
Wild-
Vermilion.
Sable.
sable.
type.
~
~ +----------+---------+------+----------+------+
149
16
29
3
3
150
13
17
2
2
151
37
63
7
2
+---------+------+----------+------+
Total.
66
109
12
8
+----------+---------+------+----------+------+
+--------------------------------------------------------------------+
F_2 males.
+----------------+---------------+-----------------+-----------------+
f_a
f_a v s
f_a s
f_a v
------
--+----
----+-
--+--+--
v s
v
s
+------+---------+---------+-----+------+----------+----------+------+
Facet.
Vermilion
Facet
Wild-
Facet
Vermilion.
Facet
Sable.
~
sable.
vermilion
type.
sable.
vermilion.
~
sable.
+------+---------+---------+-----+------+----------+----------+------+
17
10
8
12
2
..
2
1
..
10
9
..
1
..
..
..
38
23
12
26
2
8
4
1
+------+---------+---------+-----+------+----------+----------+------+
55
43
29
38
5
8
6
2
+------+---------+---------+-----+------+----------+----------+------+
LINKAGE OF EOSIN, FACET, AND VERMILION.
In order to obtain more accurate information on the location of facet, a facet male was mated to an eosin vermilion female. The F_1 females were mated singly to wild males and they gave the results shown in table 60. The F_2 females were not counted, since they do not furnish any information.
The evidence of table 60 places facet at 1.1 units to the right of eosin, or at 2.2.
TABLE 60.--_P_1 eosin vermilion_ [female] _facet_ [male]. _F_1 wild-type_ [female] _wild_ [male].
+----------+-----------------+-----------------+-----------------+
w^c v
w^c f_a
w^c
-------
--+----
----+-
f_a
v
f_a v
Reference.+----------+------+------+----------+------+----------+
Eosin
Facet.
Eosin
Vermilion.
Eosin.
Facet
vermilion.
facet.
vermilion.
+----------+----------+------+------+----------+------+----------+
512
43
43
..
1
13
16 ~
513
28
35
..
2
19
5 ~
514
18
31
1
..
17
11
515
18
60
..
..
20
15
516
10
31
..
..
7
12
517
24
34
..
..
10
12
518
44
38
1
1
23
22
+----------+----------+------+------+----------+------+----------+
Total.
185
272
2
4
109
93
+----------+----------+------+------+----------+------+----------+
+----------------+------+----------------------------+
w^c f_a v
--+---+--
Cross-over values.
+----------+-----+Total.+------+----------+----------+
Eosin
Wild-
Eosin
Facet
Eosin
facet
type.
facet.
vermilion.
vermilion.
vermilion.
+----------+-----+------+------+----------+----------+ ~ ..
..
116
....
....
....
~ ..
..
89
....
....
....
..
..
78
....
....
....
..
..
113
....
....
....
..
..
60
....
....
....
..
..
80
....
....
....
..
1
130
....
....
....
+----------+-----+------+------+----------+----------+
..
1
666
1.05
30.5
31.3
+----------+-----+------+------+----------+----------+
{78}
LETHAL SC.
The third of the lethals which Miss Stark found (Stark, 1915) while she was testing the relative frequency of occurrence of lethals in fresh and inbred wild stocks arose in April 1914 in stock caught in 1910. Females heterozygous for this lethal, lethal _sc_, were mated to white males and the daughters were back-crossed to white males. Half of the daughters gave lethal s.e.x-ratio, and these gave 1,405 cross-overs in a total of 3,053 males, from which the amount of crossing-over between white and lethal _sc_ has been calculated as 46 per cent.
By reference to table 65 it is seen that white and bar normally give only about 44 per cent of crossing-over in a two-locus experiment; lethal _sc_ then is expected to be situated at least as far to the right as bar.
Females heterozygous for lethal _sc_ were therefore crossed to bar males, and their daughters were tested. The lethal-bearing daughters gave 144 cross-overs in a total of 1,734 males, that is, bar and lethal _sc_ gave 8.3 per cent of crossing-over. Lethal _sc_ therefore lies 8.3 units beyond bar or at about 66.5. The cross-over value sable lethal _sc_ was found to be 23.5 (387 cross-overs in a total of 1,641 males) which places the lethal at 43+23.5, or at 66.5. We know from other data that there is enough double crossing-over in the distance which gives an experimental value of 23.5 per cent, so that the true distance is a half unit longer or the locus at 67.0 is indicated by the 1,641 males of the sable lethal experiment. In a distance so short that the experimental value is only 8.3 per cent there is, as far as we have been able to determine, no double crossing-over at all, or at most an amount that is entirely negligible, so that a locus at 57+8.3 or 65.3 is indicated by the 1,734 males of the bar lethal experiment. To get the value indicated by the total data the cases may be weighted, that is, the value 65.3 may be multiplied by 1,734, and 67.0 may be multiplied by 1,641. The sum of these two numbers divided by the sum of 1,734 and 1,641 gives 66.2 as the locus indicated by all the data available. This method has been used in every case where more than one experiment furnishes data upon the location of a factor. In constructing the map given in diagram I rather complex balancings were necessary.
LETHAL SD.
The fourth lethal which Miss Stark found (May 1914) in the inbred stocks of _Drosophila_ has not been located by means of linkage experiments. It is interesting in that the males which receive the lethal factor sometimes live long enough to hatch. These males are extremely feeble and never live more than two days. There is, as far as can be seen, no anatomical defect to which their extreme feebleness and early death can be attributed. {79}
FURROWED.
In studying the effect of hybridization upon the production of mutations in _Drosophila_, F. N. Duncan found a s.e.x-linked mutation which he called "furrowed eye" (Duncan 1915). The furrowed flies are characterized by a foreshortening of the head, which causes the surface of the eye to be thrown into irregular folds with furrows between. The spines of the scutellum are stumpy, a character which is of importance in cla.s.sification, since quite often flies occur which have no noticeable disturbance of the eyes.
ADDITIONAL DATA FOR YELLOW, WHITE, VERMILION, AND MINIATURE.
Considerable new work has been done by various students upon the linkage of the older mutant characters, namely, yellow, white, vermilion, and miniature. We have summarized these new data, and they give values very close to those already published. We have included in the white miniature data those published by P. W. Whiting (Whiting 1913). {80}
SUMMARY OF THE PREVIOUSLY DETERMINED CROSS-OVER VALUES.
The data of the earlier papers, namely, Dexter, 1912; Morgan, 1910_c_, 1911_a_, 1911_f_, 1912_f_, 1912_g_; Morgan and Bridges, 1913; Morgan and Cattell, 1912 and 1913; Safir, 1913; Sturtevant, 1913 and 1915; and Tice, 1914, have been summarized in a recent paper by Sturtevant (Sturtevant, 1915) and are given here in table 64. Our summary combines three summaries of Sturtevant, viz, that of single crossing-over and two of double crossing-over.
TABLE 64.--_Previously published data summarized from Sturtevant, 1915_.
+------------------------+--------+-------------+------------+
Factors.
Total.
Cross-overs.
Cross-over
values.
+------------------------+--------+-------------+------------+
Yellow white.
46,564
498
1.07
Yellow vermilion.
10,603
3,644
33.4
Yellow miniature.
18,797
6,440
34.3
Yellow rudimentary.
2,563
1,100
42.9
Yellow bar.
191
88
46.1
White vermilion.
15,257
4,910
32.1
White miniature.
41,034
13,513
32.8
White rudimentary.
5,847
2,461
42.1
White bar.
5,151
2,267
44.0
Vermilion miniature.
5,329
212
4.0
Vermilion rudimentary.
1,554
376
24.1
Vermilion bar.
7,514
1,895
25.2
Miniature rudimentary.
12,567
2,236
17.8
Miniature bar.
3,112
636
20.4
Rudimentary bar.
159
7
4.4
+------------------------+--------+-------------+------------+
{83}
SUMMARY OF ALL DATA UPON LINKAGE OF GENS IN CHROMOSOME I.
In table 65 all data so far secured upon the s.e.x-linked characters are summarized. These data include the experiments previously published in the papers given in the bibliography and the experiments given here. The data from experiments involving three or more loci are calculated separately for each value and included in the totals.
TABLE 65.--_A summary of all linkage data upon chromosome I_.
+----------------------------+----------+--------------+------------+
Gens.
Total.
Cross-overs.
Cross-over
values.
+----------------------------+----------+--------------+------------+
Yellow lethal 1.
131
1
0.8
Yellow lethal 1_b_.
744
6
0.8
Yellow white.
81,299
875
1.1
Yellow abnormal.
15,314
299
2.0
Yellow bifid.
3,681
201
5.5
Yellow club.
525
93
17.7
Yellow vermilion.
13,271
4,581
34.5
Yellow miniature.
21,686
7,559
34.3
Yellow sable.
1,600
686
42.9
Yellow rudimentary.
2,563
1,100
42.9
Yellow bar.
626
300
47.9
Lethal 1 white.
1,763
7
0.4
Lethal 1 miniature.
814
323
39.7
Lethal 1_b_ white.
846
0
0.0
White facet.
666
7
1.1
White abnormal.
16,300
277
1.7
White bifid.
23,595
1,260
5.3
White lethal 2.
8,011
767
9.6
White club.
2,251
321
14.3
White lethal _sb_.
3,678
572
15.6
White lemon.
241
35
14.5
White depressed.
59
12
20.3
White lethal _sa_.
1,150
256
22.2
White vermilion.
27,962
8,532
30.5
White reduplicated.
418
121
28.9
White miniature.
110,701
31,071
33.2
White furrowed.
208
63
30.3
White sable.
2,511
1,032
41.2
White rudimentary.
6,461
2,739
42.4
White forked.
3,664
1,676
45.7
White bar.
5,955
2,601
43.6
White fused.
430
186
43.3
White lethal _sc_.
3,053
1,406
46.0
Facet vermilion.
852
278
32.6
Facet sable.
186
80
43.0
Bifid vermilion.
2,724
849
31.1
Bifid miniature.
219
67
30.6
Bifid rudimentary.
899
384
42.7
Bifid forked.
306
130
42.5
Lethal 2 vermilion.
1,400
248
17.7
Lethal 2 miniature.
6,752
1,054
15.4
Club lethal 3.
222
29
13.0
Club vermilion.
5,558
1,047
18.8
Lethal _sb_ miniature.
3,678
733
19.9
Lemon vermilion.
241
29
12.0
{84}
Shifted vermilion.
1,007
155
15.5
Shifted bar.
242
76
31.4
Depressed vermilion.
59
10
17.0
Depressed bar.
464
176
38.0
Lethal 3 vermilion.
1,549
105
6.8
Lethal 3 miniature.
1,481
138
9.3
Vermilion dot.
57
0
0.0
Vermilion reduplicated.
667
11
1.7
Vermilion miniature.
10,155
317
3.1
Vermilion furrowed.
240
9
3.8
Vermilion sable.
9,209
929
10.1
Vermilion rudimentary.
1,554
376
24.1
Vermilion forked.
665
163
24.5
Vermilion bar.
23,522
5,612
23.9
Vermilion fused.
9,252
2,390
25.8
Reduplicated bar.
583
120
20.6
Miniature furrowed.
208
7
3.4
Miniature sable.
1,855
125
6.7
Miniature rudimentary.
12,786
2,284
17.9
Miniature bar.
3,112
636
20.5
Furrowed sable.
209
12
5.7
Furrowed forked.
209
40
19.1
Furrowed bar.
240
43
17.9
Sable rudimentary.
663
95
14.3
Sable forked.
872
140
16.0
Sable bar.
7,524
1,036
13.8
Sable lethal _sc_.
1,641
387
23.6
Rudimentary forked.
1,456
20
1.4
Rudimentary bar.
664
15
2.3
Forked bar.
1,706
8
0.5
Forked fused.
1,201
37
3.1
Bar fused.
8,768
222
2.5
Bar lethal _sc_.
1,734
144
8.3
+----------------------------+----------+--------------+------------+
