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Tham khảo tài liệu 'sat ii biology episode 1 part 6', ngoại ngữ, ngữ pháp tiếng anh phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | GENETICS MENDEL AND HEREDITY T t T t T TT Tt 1100 t Tall T TT Tt If T TT Tt Ift Tt t t 75 Tall Monohybrid Cross Incorrect Test Crosses t t T Tt Tt T A or I t T t t t T t t t If TT 100 Tall If Tt 50 Tall Monohybrid Cross Correct Test Crosses Test Crosses in Monohybrids Monohybrid does not refer to the fact that each member involved in the cross need be hybrid. It refers to the fact that individuals homozygous for both the dominant and the recessive trait when crossed will result in hybrids. Another way to say it is that monohybrid crosses reflect one of each trait the dominant and the recessive. We also use this to refer to a hybrid individual who has one dominant allele and one recessive allele. The classic monohybrid results of a phenotypic ratio of 3 1 and genotypic ratio of 1 2 1 are noted below. t Tt tt Genotype 1 2 1 1 -TT 2-Tt 1 -tt Phenotype 3 1 Tall - 3 Short -1 Monohybrid Cross Results Peterson s SAT II Success Biology E M www.petersons.com CHAPTER 4 AB Ab aB ab AB AA BB AA Bb Aa BB Aa Bb Ab AA Bb AA bb Aa Bb Aa bb aB Aa BB Aa Bb aa BB aa Bb ab Aa Bb Aa bb aa Bb aa bb Genotype AABB 1 AABb 2 AaBB 2 AaBb 4 AAbb 1 Aabb 2 aaBB 1 aaBb 2 aabb 1 Phenotype A B trait 9 A b trait 3 a B trait 3 a b trait 1 Dihybrid Cross Dihybrid Crosses A cross potentially hybrid for two traits dihybrid crosses still hold true to Mendel s laws there are simply more gametes possible and more offspring illustrated above . The typical true genotypic ratio is cumbersome to note here although it is illustrated and the typical true dihybrid phenotype ratio is the classic 9 3 3 1. If the traits are A or a and B or b the phenotypic nine would produce all AB appearing the first three might be Ab appearing making the second three aB appearing and the one would be represented by ab appearing individuals. RR X ww red white RW pink 100 RW X RW pink pink RR RW ww red pink white 25 50 25 Incomplete Dominance Incomplete Dominance Characteristics intermediate between parental extremes are shown the
