. Genetics in relation to agriculture. Livestock; Heredity; Variation (Biology); Plant breeding. 198 GENETICS IN RELATION TO AGRICULTURE mating, simplex woman {BX) (bX) by color-blind man (bX) Y, or by the still less frequent mating of color-blind woman {bX) {bX) by color-blind man (bX) Y, in which latter case all the offspring whether sons or daughters are color-blind. A considerable list of other sex-linked factors demon- strate beyond question that the inheritance of sex and the distribution of sex-linked factors in man is strictly analogous to that which we have found to obtain in Drosophi
. Genetics in relation to agriculture. Livestock; Heredity; Variation (Biology); Plant breeding. 198 GENETICS IN RELATION TO AGRICULTURE mating, simplex woman {BX) (bX) by color-blind man (bX) Y, or by the still less frequent mating of color-blind woman {bX) {bX) by color-blind man (bX) Y, in which latter case all the offspring whether sons or daughters are color-blind. A considerable list of other sex-linked factors demon- strate beyond question that the inheritance of sex and the distribution of sex-linked factors in man is strictly analogous to that which we have found to obtain in Drosophila. Non-disjunctioa in Drosophila.—Of particular interest from the standpoint of the inheritance of sex and of the relation between factors and the chromosomes are the results which Bridges has obtained from his extensive in- vestigations of non-disjunction in Drosophila. The investigations on non-disjunction had their origin in certain "exceptions" which ap- peared from time to time in cultures of Drosophila. Ordinarily in the case of sex- linked characters when a female with the recessive character is mated to a male with the dominant character all the females in Fi exhibit the dominant sex-linked character and all the males the recessive character. The reason for this fact has been explained already, but it will be clearly apparent from a consideration of Fig. 89, which is a diagram of the results of crosses between vermilion females and red males. The vermilion factor V is borne by the sex chromosomes, and since the males from crosses between vermilion females and red males receive their only A'-chromosome from the mother they should all be vermilion-eyed. The females from such a cross receive from the father an X-chromosome bearing the dominant allelomorph of v, consequently they should all be red-eyed. In the great majority of cases, this is the result actuallj^ obtained from such matings, but occasionally, about once in 1700 individuals, an exception, a vermi
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