. Genetics in relation to agriculture. Livestock; Heredity; Variation (Biology); Plant breeding. 96 GENETICS IN RELATION TO AGRICULTURE fore, greatly matter what methods are adopted so long as they represent clearly and adequately the operation of these principles. It is necessary for the student to familiarize himself with at least some of the more widely employed methods, remembering that with the basic principles clearly in mind, it should be possible to interpret very easily the methods employed in the presentation of any body of Mendelian data. For ordinary work it is well to have a defin
. Genetics in relation to agriculture. Livestock; Heredity; Variation (Biology); Plant breeding. 96 GENETICS IN RELATION TO AGRICULTURE fore, greatly matter what methods are adopted so long as they represent clearly and adequately the operation of these principles. It is necessary for the student to familiarize himself with at least some of the more widely employed methods, remembering that with the basic principles clearly in mind, it should be possible to interpret very easily the methods employed in the presentation of any body of Mendelian data. For ordinary work it is well to have a definite system of interpreting problems. In the following treatment only cases involving the category of independently segregating pairs of factors are considered, but it should be possible to extend the system without great difficulty to other categories as will be pointed out in those sections dealing with such categories. When an individual is heterozygous for one pair of factors two types of gametes are possible. If the factors involved are repre- sented by A and a, the genotypic constitution of such an individual is Aa, and the two types of gametes are A and a. If an in- dividual is heterozygous for two jDairs of factors, its genotypic formula will be AaBb, and there are then possible four different kinds of gametes, namely AB, Ab, aB and ab. As the number of heterozygous factors increases, therefore, the number of possible combinations of factors increases geometrically so that it is necessary to adopt a method of writing clown these possible combinations. The method of dichotomy may be used in such cases, and the diagram. Fig. 47, explains its operation without further comment. With as few as five pairs of factors, therefore, there are possible no less than thirty-two diiferent kinds of gametes as follows:. Fig. 47.—Method of writing all possible coniljiiiations of any number of pairs of factors. ABCDE AbCDE aBCDE abCDE ABCDe AbCDe aBCDe abCDe ABCdE AbCdE oBCdE ahCdE ABCde
Size: 1164px × 2148px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksu, booksubjectplantbreeding
