Sex-linked Inheritance In Drosophila 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} s.h.i.+fted vermilion. 1,007 155 15.5 s.h.i.+fted 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 +----------------------------+----------+--------------+------------+