Inheritance of Characteristics in Domestic Fowl

by Charles Benedict Davenport

Table 34.—Distribution of boot-grade in the F₂ generation of booted × non-booted poultry—Continued.

SILKIE CROSSES.
Pen No.	Mother.				Father.				Boot-grade in offspring.
	No.	Gen.	Races.	Gr.	No.	Gen.	Races.	Gr.	0	1	2	3	4	5	6	7	8	9	10	Aver- age.	P. ct. absent.
709	1955	F1	Silkie × Spanish	5	1578	F1	Silkie × Spanish	0	5	1	2	1	1	1	1	0	0	0	0	1.92	41.7
753	1966	F1	Silkie × Min	0	2573	F1	Min. × Silkie	0	19	4	2	2	...	2	2	2	1	...	...	1.71	55.9
709	1963	F1	Silkie × Spanish	7	1578	F1	Silkie × Spanish	0	23	6	1	6	7	...	...	...	...	...	...	1.26	53.5
753	2575	F1	Silkie × Min	0	2573	F1	Silkie × Min.	0	15	3	7	...	...	...	...	...	...	...	...	0.68	60.0
753	2071	F1	Do.	0	2573	F1	Do.	0	23	4	6	...	...	...	...	...	...	...	...	0.49	69.7
709	1453	F1	Do.	1	1578	F1	Silkie × Spanish	0	24	11	3	...	...	...	...	...	...	...	...	0.45	63.2
709	2223	F1	Silkie × Spanish	0	1578	F1	Do.	0	32	7	3	...	...	...	...	...	...	...	...	0.31	76.2
			Totals (227)						141	36	24	9	8	3	3	2	1	0	0	0.87	62.2
830	4082	F1	Silkie × W. Legh	2	3947	F1	Silkie × W. Legh	1	11	8	...	7	1	...	...	...	...	...	...	1.22	40.7
830	4079	F1	Do.	0	3947	F1	Do.	1	18	7	6	3	...	...	...	...	...	...	...	0.82	53.0
830	5379	F1	Do.	0	3947	F1	Do.	1	18	4	5	3	...	...	...	...	...	...	...	0.77	60.0
830	4081	F1	Do.	0	3947	F1	Do.	1	24	6	10	1	...	...	...	...	...	...	...	0.71	58.5
830	5374	F1	Do.	0	3947	F1	Do.	1	11	3	3	1	...	...	...	...	...	...	...	0.67	61.1
830	3946	F1	Do.	0	3947	F1	Do.	1	19	1	...	...	1	...	...	...	...	...	...	0.24	90.5
			Totals (170)						101	29	24	14	2	0	0	0	0	0	0	0.75	59.4

The distribution of table 35 is characterized by its large variability. Although the numbers are small, there are evidences of two modes, one between grades 3 and 6, and the other at from 8 to 10; these evidently correspond to the modes of the typical Silkie and the typical Cochin respectively or to DR and RR types of booting respectively. The distribution of table 35 is additional evidence of the heterozygous nature of the Silkie boot.

Table 35.—Distribution of boot-grades in Silkie × Cochin crosses.

Pen No.	Mother.				Father.				Boot-grades in offspring.
	No.	Gen.	Races.	Gra.	No.	Gen.	Races.	Gra.	0	1	2	3	4	5	6	7	8	9	10	Aver- age.	P. ct. abs.
821	5925	F1	Silk. × Coch.	7	6095	F1	Silk. × Coch.	7	...	...	...	...	1	...	...	1	3	1	1	7.7	0.0
821	7408	F1	Do.	4	6095	F1	Do.	7	...	...	...	1	2	2	3	...	2	1	2	6.5	0.0
821	7413	F1	Do.	3	6095	F1	Do.	7	2	0	3	1	0	1	1	0	0	1	1	3.9	20.0
821	7416	F1	Do.	5	6095	F1	Do.	7	...	...	...	3	1	0	4	0	3	3	2	6.8	0.0
821	7417	F1	Do.	...	6095	F1	Do.	7	...	...	...	...	...	...	...	1	...	1	4	9.3	0.0
821	7418	F1	Do.	4	6095	F1	Do.	7	...	...	1	...	2	1	1	1	1	...	1	5.8	0.0
821	7423	F1	Do.	6	6095	F1	Do.	7	...	...	...	1	...	2	...	2	2	...	2	7.0	0.0
821	7428	F1	Do.	...	6095	F1	Do.	7	1	...	...	...	...	1	...	...	1	...	...	4.3	33.3
821	7429	F1	Do.	8	6095	F1	Do.	7	...	...	...	1	1	1	...	...	...	1	1	6.2	0.0
			Totals (77)						3	0	4	7	7	8	9	5	12	8	14	6.42	3.90
									29						48

We are now in a position to consider the effect of back crosses (table 36). The contrast between the totals in tables 36 and 37 is very great. The strict Mendelian expectation is: in the DR × D crosses 50 per cent DD (clean-footed) and 50 per cent heterozygous, which, with imperfect dominance, might be expected to show foot-feathering. Actually about 46 per cent are clean-footed. In the DR × R crosses expectation is that 50 per cent certainly (the extracted recessives) and 50 per cent more possibly will have the shanks feathered, on account of imperfect dominance of the heterozygotes. Actually all have feathered feet. These statistics thus confirm the view of the dominance of the inhibiting factor. Were clean shank recessive, then the DR × R crosses must give 50 per cent clean-footed and probably over. The actual result, none clean-footed, is not in accord with the latter assumption.

Table 36.—Distribution of boot-grade in DR × D (non-booted) crosses.

Pen No.	Mother.				Father.				Boot-grade in offspring.
	No.	Gen.	Races.	Grade.	No.	Gen.	Race.	Grade.	Present.	Slight.	Absent.	Per cent. present.
653	508	F1	Wh. Legh. × Bf. Coch.	Pr.	117	P.	Game.	0	3	4	6	46.2
653	508	F1	Do.	Pr.	116	P.	Do.	0	6	5	4	26.7
653	577	F1	R × Bf. Coch.	3	117	P.	Do.	0	1	0	7	87.5
653	577	F1	Do.	3	116	P.	Do.	0	1	3	2	33.3
653	587	F1	Do.	1	117	P.	Do.	0	1	2	4	57.1
653	587	F1	Do.	1	116	P.	Do.	0	3	3	2	25.0
653	635	F1	Do.	3	117	P.	Do.	0	...	1	6	85.7
653	635	F1	Do.	3	116	P.	Do.	0	2	2	1	20.0
653	652	F1	Do.	5	117	P.	Do.	0	5	8	4	23.5
653	652	F1	Do.	5	116	P.	Do.	0	1	2	2	40.0
653	691	F1	Do.	Pr.	117	P.	Do.	0	2	2	1	20.0
653	705	F1	Do.	2	117	P.	Do.	0	3	2	5	50.0
653	705	F1	Do.	2	116	P.	Do.	0	1	1	5	71.4
653	713	F1	Do.	Pr.	117	P.	Do.	0	...	0	4	100.0
653	713	F1	Do.	Pr.	116	P.	Do.	0	1	1	3	60.0
653	760	F1	Do.	Pr.	117	P.	Do.	0	2	2	6	60.0
653	760	F1	Do.	Pr.	116	P.	Do.	0	0	3	2	40.0
653	799	F1	Do.	3	117	P.	Do.	0	2	0	3	60.0
			Total (143)						34	42	67	46.9
661	635	F1	Bf. Coch. × Game.	Pr.	466	P.	Game.	0	1	...	2	66.7
661	635	F1	Do.	Pr.	428	P.	Do.	0	2	...	1	33.3
661	691	F1	Do.	Pr.	466	P.	Do.	0	2	...	2	50.0
661	691	F1	Do.	Pr.	428	P.	Do.	0	2	...	1	33.3
661	799	F1	Do.	Pr.	466	P.	Do.	0	3	...	2	40.0
661	799	F1	Do.	Pr.	428	P.	Do.	0	4	...	1	20.0
			Total (23)						14	0	9	39.1
			Grand Total (166)						48	42	76	45.8

Table 37.—Distribution of boot-grade in DR × RR (booted) crosses.

[A]Pure-blooded Silkie assumed heterozygous to boot.
Pen No.	Mother.				Father.				Boot-grade in offspring.
	No.	Gen.	Race.	Gr.	No.	Gen.	Race.	Gr.	0	1	2	3	4	5	6	7	8	9	10
851	838	P.	Cochin.	8	7526	[A]F1	Silkie.	3	...	...	...	3	2	4	3	...	...	2	2
851	840	P.	Do.	10	7526	F1	Do.	3	...	...	...	...	1	...	1	...	...	1	...
851	841	P.	Do.	10	7526	F1	Do.	3	...	...	...	...	1	...	1	...	1	...	...
851	1002	P.	Do.	8	7526	F1	Do.	3	...	...	...	3	1	2	1	2	3	1	1
851	2073	P.	Do.	7	7526	F1	Do.	3	...	...	1	1	1	...	1	1	1	3	2
851	2299	P.	Do.	9	7526	F1	Do.	3	...	...	...	...	2	2	1	1	...	...	2
851	3410	P.	Do.	9	7526	F1	Do.	3	...	...	...	...	...	4	3	2	1	5	1
851	5567	P.	Do.	9	7526	F1	Do.	3	...	...	...	...	2	...	...	...	3	3	5
851	6956	P.	Do.	8	7526	F1	Do.	3	...	...	...	...	3	3	...	2	2	...	5
			Totals (99)						0	0	1	7	13	15	11	8	11	15	18