Double-crossover Classes
The double-crossover classes show that the Su gene recombined with
the Lz and Gl genes. Therefore Su is in the middle, between Lz and Gl.
Result
is GllzSu and glLzsu.
Result is GllzSu and glLzsu.
Result is GllzSu and glLzsu.
Result is GllzSu and glLzsu.
Result is GllzSu and glLzsu.
Result is GllzSu and glLzsu.
Result is GllzSu and glLzsu.
If Lz is the middle locus, then the double crossover and least frequent
classes would involve an exchange of Lz.
If
Gl is in the middle, then double-crossover would result in LzglSu and
lgGlsu as the least frequent classes.
Result is GllzSu and glLzsu.
Result is GllzSu and glLzsu.
Result is GllzSu and glLzsu.
If
Su is in the middle, then double-crossover would result
in GlsuLz and glSulz as the least frequent classes.
Result is GllzSu and glLzsu.
Result is GllzSu and glLzsu.
Result is GllzSu and glLzsu.
We can use three-point testcrosses to map gene order.
We can now summarize the data:
LzSuGl
lzsugl |
286
272 |
Parental
types, non-crossover |
Lzsugl
lzSuGl |
40
33 |
Single
crossover between Lz and Su |
LzSugl
lzsuGl |
59
44 |
Single
crossover between Su and Gl |
LzsuGl
lzSugl |
4
2 |
Double-crossover |
| Total |
740 |
|
The reciprocal products that result from a cross over occur with approximately
equal frequency. Deviations are due to sampling.
