Part 4
w^e V s --+--------------------------------------------------+--------------+ X X --+--------------------------------------------------+--------------+ W v S
DIAGRAM II.--The upper line represents an X chromosome, the lower line its mate. The cross connecting lines indicate crossing-over between pairs of factors.
w^e s {Eosin sable.
Non-cross-overs -------------------------- { v {Vermilion.
w^e v {Eosin vermilion.
Single cross-overs ------------+------------- { s {Sable.
w {Eosin.
-----------------------+-- { v s {Vermilion sable.
w^e v s {Eosin vermilion sable.
Double cross-overs ------------+----------+-- { {Wild-type.
If we consider the female cla.s.ses of table 11, we get information as to the cross-over value of eosin and sable, namely, 42 units. The male cla.s.ses will be considered in connection with the cross that follows.
The next experiment involves the same three gens which now enter in different relations. A double recessive, eosin vermilion (gray) female {39} was mated to (red red) sable males and gave 202 wild-type[5] females and 184 eosin vermilion males. Two F_1 pairs gave the results shown in table 12 (the four cla.s.ses of females not being separated).
TABLE 12.--_P_1 eosin vermilion F_1 wild-type [female] F_1 eosin vermilion [male] [male]._
+------+--------+-------------------------------------------------------+
F_2 males.
+-------------+-------------+-------------+-------------+
w^e v
w^e s
w^e v s
w^e
-----------
-----+-----
--------+--
----+---+--
Refer-
F_2
s
v
v s
ence.
females.+------+------+------+------+------+------+------+------+
Eosin
Eosin
verm-
Wild-
Verm-
verm-
Sable.
Eosin
Verm-
ilion
type.
Eosin.
ilion
ilion.
[male]
sable.
ilion.
sable.
[male]
[male]
sable.
[male]
[male]
[male]
[male]
[male]
+------+--------+------+------+------+------+------+------+------+------+
59 C
133
40
33
7
16
5
5
2
1
61 C
101
34
26
8
11
3
7
1
0
+--------+------+------+------+------+------+------+------+------+
Total
234
74
59
15
27
8
12
3
1
+------+--------+------+------+------+------+------+------+------+------+
If we combine the data for males given in table 12 with those of table 11, we get the following cross-over values. Eosin vermilion, 32; vermilion sable, 12; eosin sable, 41.
{40}
LINKAGE OF MINIATURE AND SABLE.
The miniature wing has been described (Morgan, Science, 1911) and the wing figured (Morgan, Jour. Exp. Zool., 1911). The gen for miniature lies about 3 units to the right of vermilion, so that it is still closer to sable than is vermilion. The double recessive, miniature sable, was made up, and males of this stock were bred to wild females (long gray). The wild-type daughters were back-crossed to double recessive males and gave the results (ma.s.s cultures) shown in table 13.
TABLE 13.--_P_1 wild [female] [female] miniature sable [male] [male]. B.
C. F_1 wild-type [female] [female] miniature sable [male] [male]._
+-----------+---------------------+-----------------+-------+-------+
Non-cross-overs.
Cross-overs.
Cross-
Reference.+----------+----------+----------+------+ Total.
over
value.
Miniature
Wild-type.
Miniature.
Sable.
sable.
+-----------+----------+----------+----------+------+-------+-------+
38 I
245
283
15
17
560
6
43 I
191
236
13
18
458
7
46 I
232
274
24
21
551
8
+----------+----------+----------+------+-------+-------+
Total
668
793
52
56
1,569
7
+-----------+----------+----------+----------+------+-------+-------+
Since the results for the male and the female cla.s.ses are expected to be the same, the s.e.xes were not separated. The combined data give 7 per cent of crossing-over between miniature and sable.
LINKAGE OF VERMILION, SABLE, AND BAR.
Bar eye has been described by Mrs. S. C. Tice (1914). It is a dominant s.e.x-linked character, whose locus, lying beyond vermilion and sable, is near the right end of the chromosome series, that is, at the end opposite yellow.
In the first cross of a balanced series of experiments for the gens vermilion, sable, and bar, vermilion (gray not-bar) entered from one side ([female]) and (red) sable bar from the other ([male]). The daughters were bar and the sons vermilion. The daughters were back-crossed singly to the triple recessive males vermilion sable (not-bar), and gave the data included in table 14.
In the second cross, vermilion sable (not-bar) went in from one side ([female]) and (red, gray) bar from the other. The daughters were bar and the sons were vermilion sable. Since these sons have the three recessive factors, inbreeding of F_1 is equivalent to a triple back-cross. The results are given by pairs in table 15. {41}
TABLE 14.--_P_1 vermilion [female] [female] sable bar [male] [male]. B.
C. F_1 bar [female] vermilion sable [male] [male]._
+------+------------+-----------+------------+-----------+
v
v s B'
v B'
v s
----------
---+-----
-----+----
--+--+---
s B'
s
B'
+------+-----+-----+-----+-----+------+------+----+
Refer-
Verm-
ence.
Verm-
Sable
ilion
Wild-
Verm-
Ver-
ilion.
bar.
sable
type.
ilion
Sable.
milion
Bar.
bar.
bar.
sable.
+------+------+-----+-----+-----+-----+------+------+----+
147 I
81
66
12
15
15
18
~
148 I
103
108
4
19
11
11
~
149 I
97
88
10
8
17
17
1
1
150 I
95
75
10
11
21
22
1
1
151 I
116
96
11
15
23
26
2
89
89
94
10
19
15
11
1
90
49
50
4
8
15
14
91
104
88
13
15
12
12
+------+-----+-----+-----+-----+------+------+----+
Total.
734
665
74
110
129
131
3
4
+------+------+-----+-----+-----+-----+------+------+----+
+------+------+------------------+
Cross-over values.
+------+-----+-----+
Refer-
Total.
ence.
Verm-
Verm-
ilion
Sable
ilion
sable.
bar.
bar.
+------+------+------+-----+-----+
~147 I
207
13
16
29
~148 I
256
9
9
18
149 I
239
8
15
22
150 I
236
10
19
27
151 I
289
10
18
26
89
239
13
11
23
90
140
9
21
29
91
244
11
10
21
+------+------+-----+-----+
Total.
1,850
10
14
24
+------+------+------+-----+-----+
TABLE 15.--_P_1 vermilion sable [female] [female] bar [male] [male]. B.
C. F_1 bar [female] vermilion sable [male] [male]._
+------+----------+------------+-----------+------------+
v s
v B'
v s B'
v
--------
---+------
-----+---
--+---+---
B'
s
s B'
+------+---+-----+------+-----+-----+------+-----+
Refer-
Verm-
ence.
Verm-
Verm-
ilion
Wild-
Verm-
Sable
ilion
Bar
ilion
Sable.
sable
type.
ilion.
bar.
sable.
bar.
bar.
+------+------+---+-----+------+-----+-----+------+-----+
105 I
41
75
10
4
5
11
~
106 I
59
122
16
13
11
17
~
107 I
92
98
8
12
16
10
116 I
111
149
19
16
20
19
1
117 I
92
117
16
14
15
18
126 I
96
160
13
13
17
35
127 I
117
124
13
25
24
30
1
+------+---+-----+------+-----+-----+------+-----+
Total
608
845
95
97
108
140
1
1
+------+------+---+-----+------+-----+-----+------+-----+
+------+------+------------------+
Cross-over values.
+------+-----+-----+
Refer-
Total.
ence.
Verm-
Verm-
ilion.
Sable
ilion
sable.
bar.
bar.
+------+------+------+-----+-----+ ~105 I
146
10
11
21
~106 I
238
12
12
24
107 I
236
9
11
20
116 I
335
11
12
22
117 I
272
11
12
23
126 I
334
8
15
23
127 I
334
12
16
28
+------+------+-----+-----+
Total
1,895
10
13
23
+------+------+------+-----+-----+
{42}
In the third cross, vermilion (gray) bar entered from one side ([female]) and (red) sable (not-bar) from the other ([male]). The daughters are bar and the sons vermilion bar. The daughters were back-crossed singly to vermilion sable males and gave the data in table 16.
TABLE 16.--_P_1 vermilion bar_ [female] [female] _sable_ [male] [male].
_B. C. F_1 bar_ [female] _vermilion sable_ [male] [male].
+-----------+--------------+------------+-------------+---------------+
v B'
v s
v
v s B'
-----
-+------
-----+--
-+---+--
Reference.
s
B'
s B'
+-------+------+------+-----+-------+-----+---------+-----+
Ver-
Sable.
Ver-
Bar.
Ver-
Sable
Vermilion
Wild-
milion
milion
milion.
bar.
sable
type.
bar.
sable.
bar.
+-----------+-------+------+------+-----+-------+-----+---------+-----+
129 I
132
147
15
15
19
21
1
1 ~
130 I
194
168
21
17
28
25
..
1 ~
131 I
121
89
10
20
26
11
1
1
137 I
139
113
19
12
33
14
..
1
138 I
131
128
11
11
28
24
1
..
139 I
83
79
4
12
17
12
..
..
+-------+------+------+-----+-------+-----+---------+-----+
Total.
800
724
80
87
151
107
3
4
+-----------+-------+------+------+-----+-------+-----+---------+-----+
+-----------+-------+-------------------------+
Reference.
Total.
Cross-over values.
+---------+-----+---------+
Vermilion
Sable
Vermilion
sable.
bar.
bar.
+-----------+-------+---------+-----+---------+ ~ 129 I
351
9
12
20
~ 130 I
454
9
12
20
131 I
279
12
14
24
137 I
331
10
15
24
138 I
334
7
16
22
139 I
207
8
14
22
+-------+---------+-----+---------+
Total.
1,956
9
14
22
+-----------+-------+---------+-----+---------+
In the fourth cross, vermilion sable bar entered from one side, and (red gray not-bar) wild type from the other. The daughters were bar and the sons vermilion sable bar. The daughters were back-crossed singly to vermilion sable males, with the results shown in table 17.
TABLE 17.--_P_1 vermilion sable bar_ [female] [female] _wild_ [male]
[male]. _B. C. F_1 bar_ [female] _vermilion sable_ [male] [male].
+-----------+---------------+--------------+------------+--------------+
v s B'
v
v s
v B'
--------
-+-----
-----+--
-+-+--
Reference.
s B'
B'
s
+---------+-----+--------+-----+-------+----+-------+------+
Vermilion
Wild-
Ver-
Sable
Ver-
Bar.
Ver-
Sable.
sable
type
milion.
bar.
milion
milion
bar.
sable.
bar.
+-----------+---------+-----+--------+-----+-------+----+-------+------+
132 I
95
108
10
13
24
22
..
.. ~
133 I
112
150
18
16
26
16
1
2 ~
134 I
84
95
14
7
15
16
..
1
135 I
100
86
16
17
19
22
..
1
152 I
73
88
12
8
14
18
..
..
153 I
114
138
12
12
17
17
..
..
154 I
63
90
10
8
8
15
..
..
Total.
641
755
92
81
123
126
1
4
+-----------+---------+-----+--------+-----+-------+----+-------+------+
+-----------+------+-------------------------+
Reference.
Total.
Cross-over values.
+---------+-----+---------+
Vermilion
Sable
Vermilion
sable.
bar.
bar.
+-----------+------+---------+-----+---------+ ~ 132 I
272
9
17
25
~ 133 I
341
11
13
22
134 I
232
10
14
22
135 I
261
13
16
28
152 I
213
9
15
24
153 I
310
8
11
19
154 I
194
9
12
21
Total.
1,823
10
14
23
+-----------+------+---------+-----+---------+
{43}
In tables 14 to 17 the calculations for the three cross-over values for vermilion, sable, and bar are given for the separate cultures and for the totals. The latter are here repeated.
+-----------+-----------+---------+-----------+
From--
Vermilion
Sable
Vermilion
sable.
bar.
bar.
+-----------+-----------+---------+-----------+
Table 14
10
14
24
15
10
13
23
16
9
14
22
17
10
14
23
+-----------+-----------+---------+-----------+
The results of the different experiments are remarkably uniform. There can be no doubt that the cross-over value is independent of the way in which the experiment is made, whether any two recessives enter from the same or from opposite sides.
TABLE 18.--_Linkage of vermilion, sable, and bar with balanced viability._
+---------------------+---------+---------+---------+---------+-------+
-------
--+----
----+--
--+-+--
Total.
+---------------------+---------+---------+---------+---------+-------+
Wild-type
755
110
140
4
Vermilion
734
92
151
1
Sable
724
97
131
4
Bar
845
87
126
4
Vermilion sable
608
80
123
3
Vermilion bar
800
95
129
1
Sable bar
665
81
107
1
Vermilion sable bar
641
74
108
3
+---------+---------+---------+---------+-------+
Total
5,772
716
1,015
21
7,524
Percentage
76.7
9.53
13.49
0.28
+---------------------+---------+---------+---------+---------+-------+
In table 18 the data from each of the four separate experiments have been combined in the manner explained, so that viability is canceled to the greatest extent. The amount of each kind of cross-over appears at the bottom of the table. The total amount of crossing-over between vermilion and sable is the sum of the single (9.53) and of the double (0.28) cross-overs, which value is 9.8. Likewise the cross-over value for sable bar is 13.49 + 0.28 (= 14), and for vermilion bar is 9.53 + 13.49 (= 23).
By means of these cross-over values we may calculate the coincidence involved, which is in this case
0.0028 100 --------------------------------- = 20.8 0.0953 + 0.0028 0.1349 + 0.0028
This value shows that there actually occurs only about 21 per cent of the double cross-overs which from the values of the single cross-overs are expected to occur in this section of the chromosome. This is the result which is to be antic.i.p.ated upon the chromosome view, for if crossing-over is connected with loops of the chromosomes, and if these loops have an average length, then if the chromosomes cross over at one {44} point it is unlikely they will cross over again at another point nearer than the average length of the loop.
