The genes affecting egg production exhibit both additive genetic effects and dominant deviations. They also show non-allelic interactions. The non-allelic interaction between G and D results in low egg production.

An asymmetry in the distribution of positive and negative allels exists in the parents, which was understandable as three of the six lines included in the trial were selected for low egg production and the other three for high egg production.

There are probably present more dominant than recessive genes affecting egg Production in the parental stock used in these studies; the ratio of recessives to dominants being of the order of 1:4. Low egg production is due to recessive genes, high egg production to their dominant allels.

Dominance deviations present were largely unidirectional.

The order of dominance of the six lines used was D, B, E, C, A, F.

For keeping the X-chromosome intact, throughout the generations of testing, the balanced technique employingscute inversion No. 1 of Sinitskaya that balanced practically the entire X-chromosome as reported by. Müller and Prokofyeva (1934) was employed. TheBar gene on this chromosome acted as the marker. The stocks utilised were N-8 (normal) and b-297 (marked).

Reciprocal crosses were made between N-8 and b-297. Repeated backcrosses were made of the resulting progeny to either of the two stock flies, selecting in each case, the female containing the marked chromosome till on an average 15/16 of the autosomes of one parental stock was replaced by those of the other parental stock, while the marked X-chromosome and an unmarked X-chromosome remained intact.

At each stage of backcrossing, observations were made on fecundity, egg-length, egg-volume (calculated) and hatchability.

Results showed that in case of fecundity, the genes affecting fecundity were not necessarily more numerous on the X-chromosome than in all the autosomes taken together as suggested by Berg (1937). In fact the data showed that the contribution of the autosomes is more than that of the X-chromosome. In case of egg-length and egg-volume there was evidence to suggest the presence of a few dominant genes radically affecting egg-length in the X-chromosome. This appeared to be so in a more pointed manner in case of hatchability which was a character with practically zero heritability.

Male and female calf bearing gestations were considered separately since significant differences existed between the two in the majority of cases. h² (heritability estimate) was estimated by sib-analysis and the components of variance due to sire, dam and environment calculated, and the percentage contribution of each to the total variance estimated.

Significant variation in gestation period due to sire was found inGir andKangayam breeds only forfemale births. In case of all other breeds and herds of a breed no significant effect due to sire was found for births of either sex which suggested that the sire influence on gestation period in Indian breeds was generally small and negligible.

The contribution of the sire to the total variation in gestation period was also found to be small in general. The exceptions are theSindhi herd at Bangalore (21.6%) for male births andAmrit Mahal (23.8%) andGir (19%) animals for female births.

Estimates of h² for female births were found to be either zero, or small and negligible or large with large sampling errors that made the estimates undependable with the exception ofKankrej where the estimate was 0.55±0.09. In general, it was concluded that h² for gestation period in Indian cattle breeds was small and negligible. Where significant variation was obtained as inKankrej in our study and inHariana of Haringhata in a different study reported in the literature, it was explained as due to use of sires obtained from widely varying sources, or due to the animals being still in the process off development as dual purpose animals through selective breeding.

Blood typing of about 157 heads ofHariana and 97 heads ofJersey-Sindhi crossbreds was done with the 15 reagents.

The frequency of occurrence for theHariana andJersey-Sindhi crossbreds with respect to 15 antigens revealed highly significant differences with respect to six (C, R, W, J, M, Iz₃₃) antigens and significant difference for the Zt’ factor.

The comparisons of incidences of occurrence of blood-group factors for two herds each ofHariana, andJersey-Sindhi crossbred animals showed significant variations in their incidence amongst different herds within the same breed also.

Reciprocal crosses were made between N-2 and G-l Hies. Selecting F-l females with the marked chromosome in one case, repeated backcrosses were made with N-2 males from stock and in another case with C-l males. In each generation, the fecundity and the hatchability were noted.

Results showed that the chromosome II contained genes for fecundity and hatchability which were more than in all the other chromosomes put together.