selves in the offspring. The crosses are lled ssed differently in homozy- heterozygous individuals. This produces a con- dition called incomplete dominance. In such cases, both worked out in the same manner as indicated previously, but heterozygous offspring exhibit a phenotype interme- diate between that of the homozygous individuals. Some examples follow. Activity 2 Working Out Crosses Involving Incomplete Dominance 1. The inheritance of flower color in snapdragons illustrates the principle of incomplete dominance. The geno-type RR is expressed as a red flower, Rr yields pink flowers, and rr produces white flowers. Work out the following crosses to determine the expected phenotypes and both genotypic and phenotypic percentages. % of each phenotype: 2. In humans, the inheritance of sickle cell anemia/trait is deter- mined by a single pair of alleles that exhibit incomplete domi- nance. Individuals homozygous for the sickling gene (s) have sickle cell anemia. In double dose (ss), the sickling gene causes production of a very abnormal hemoglobin, which crystallizes and becomes sharp and spiky under conditions of oxygen deficit. Heterozygous individuals (Ss) have the sickle cell trait; they make both normal and sickling hemoglobin. Usually these individuals are healthy, but prolonged decreases in blood oxygen levels can lead to a sickle cell crisis. Individuals with the genotype SS form normal hemoglobin. Work out the following crosses: a. Genotypes of parents: RR X rr % of each genotype: % of each phenotype: b. Genotypes of parents: Rr X rr a. Parental genotypes: SS × ss % of each genotype: 45 % of each genotype: % of each phenotype: % of each phenotype: b. Parental genotypes: ss X Ss C. Genotypes of parents: Rr X Rr % of each genotype: % of each genotype: % of each phenotype:
selves in the offspring. The crosses are lled ssed differently in homozy- heterozygous individuals. This produces a con- dition called incomplete dominance. In such cases, both worked out in the same manner as indicated previously, but heterozygous offspring exhibit a phenotype interme- diate between that of the homozygous individuals. Some examples follow. Activity 2 Working Out Crosses Involving Incomplete Dominance 1. The inheritance of flower color in snapdragons illustrates the principle of incomplete dominance. The geno-type RR is expressed as a red flower, Rr yields pink flowers, and rr produces white flowers. Work out the following crosses to determine the expected phenotypes and both genotypic and phenotypic percentages. % of each phenotype: 2. In humans, the inheritance of sickle cell anemia/trait is deter- mined by a single pair of alleles that exhibit incomplete domi- nance. Individuals homozygous for the sickling gene (s) have sickle cell anemia. In double dose (ss), the sickling gene causes production of a very abnormal hemoglobin, which crystallizes and becomes sharp and spiky under conditions of oxygen deficit. Heterozygous individuals (Ss) have the sickle cell trait; they make both normal and sickling hemoglobin. Usually these individuals are healthy, but prolonged decreases in blood oxygen levels can lead to a sickle cell crisis. Individuals with the genotype SS form normal hemoglobin. Work out the following crosses: a. Genotypes of parents: RR X rr % of each genotype: % of each phenotype: b. Genotypes of parents: Rr X rr a. Parental genotypes: SS × ss % of each genotype: 45 % of each genotype: % of each phenotype: % of each phenotype: b. Parental genotypes: ss X Ss C. Genotypes of parents: Rr X Rr % of each genotype: % of each genotype: % of each phenotype:
Human Heredity: Principles and Issues (MindTap Course List)
11th Edition
ISBN:9781305251052
Author:Michael Cummings
Publisher:Michael Cummings
Chapter7: Development And Sex Determination
Section: Chapter Questions
Problem 18QP: Equalizing the Expression of X Chromosome Genes in Males and Females Males have only one X...
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