I am using y10 as a cell autonomous marker for mosaic analysis of lg2, and need to know the distance between y10 and lg2. Both mutations are recessive, and y10 dies as a white seedling. Thus, a typical mapping testcross to a double recessive homozygote is not possible. Robertson, DS mapped y10 approximately 11 map units from lg2 (Robertson, Genetics 46:649-662, 1961). Beckett, JB showed by TB translocations that y10 is distal to lg2 (J. Hered. 69:27-36, 1978). I obtained data from selfs of 5 double heterozygotes of lg2 and y10 in coupling.
 

	Phenotypes
	Parentals		Recombinants
Family	W.T.	lg y10	y10	lg
510.1 self	42	5	5	4
510.3 self	32	11	0	4
510.4 self	26	5	2	2
510.5 self	83	31	11	11
510.7 self	75	21	3	6
TOTAL	258	73	21	27

In order to calculate the recombination frequency, I used two methods, and made the assumption that recombination frequency between these 2 genes is the same in the male and female. Using the product method (Immer, Genetics 15:81-98, 1930), the recombination frequency comes out to 0.134, with a probable error of 1.3%. Using maximum likelihood (Mather, The Measurement of Linkage in Heredity, Wiley and Sons, 2nd ed., 1951), the recombination frequency comes out to 0.135, with a standard error of 1.9%.

Thus y10 is 13.4 map units distal to lg2 on chromosome 3. 

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