Concept explainers
Introduction: An allele is defined as a variant of a gene responsible for coding for a specific character. There are two different alleles for each phenotypic characteristics. One allele is dominant while the other form of the allele is recessive. The interaction between the alleles is responsible for showing phenotypic traits. Phenotypic traits are defined as the observable features, such as size, shape, color and many more.
Answer to Problem 1TY
Correct answer: Based on Mendel’s experiments, the expected
Explanation of Solution
Reason for correct answer:
According to Mendel’s experiment, when two heterozygous plants are crossed in the F2 generation, each offspring possessing even a single dominant characteristic will express the dominant gene. Of four plants, three plants should express the dominant trait. In the cross-section, only one out of every fourth plant will have both the recessive alleles and will be homozygous recessive. Such plant will express a recessive phenotype. So, the phenotypic ratio of the F2 generation will be 3:1.
Option c. is given as “3:1”.
According to Mendel’s experiments, in a single factor-cross, the expected phenotype ratio in the F2 generation is 3:1. Hence, the correct answer is option c.
Reason for incorrect answer:
Option a. is given as “1:2:1”.
The given ratio represents the genotypic ratio obtained in the F2 generation from a single-factor cross. Hence, option a. is incorrect.
Option b. is given as, “2:1”.
In the F2 generation, the phenotypic ratio obtained is three dominant phenotype expressing plants, including two heterozygous and one homozygous dominant and one recessive phenotype expressing plant. Hence, option b. is incorrect.
Option d. is given as “9:3:3:1”.
9:3:3:1 is the expected phenotypic ratio in the F2 generation from a double-factor cross. Hence, option d. is incorrect.
Option e. is given as, “4:1”.
In the F2 generation, the phenotypic ratio obtained is three dominant phenotype expressing plants, including two heterozygous and one homozygous dominant and one recessive phenotype expressing plant. Hence, option e. is incorrect.
Hence, the options a., b., d., and e. are incorrect.
According to Mendel’s experiments, the expected phenotype ratio in the F2 generation from a single-factor cross is 3:1.
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Chapter 17 Solutions
Biology