Biology
Biology
5th Edition
ISBN: 9781260487947
Author: BROOKER
Publisher: MCG
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Chapter 17, Problem 1TY
Summary Introduction

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.

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Answer to Problem 1TY

Correct answer: Based on Mendel’s experiments, the expected phenotype ratio in the F2 generation from a single-factor cross is 3:1. Hence, the correct answer is option c.

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.

Conclusion

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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Students have asked these similar questions
Mendel used dihybrid crosses to test the idea that alleles for two different characters assort independently.  In a typical dihybrid cross (such as RrTt x RrTt), what proportions of phenotypes would be expected in the offspring? Select one: a. 9:3:3:1 b. 4:4:4:4 c. 2:2 d. 3:1 e. 100% dominant phenotype
If a Mendel's dihybrid cross between two double heterogotes (AaBb  x AaBb), assuming that the dominant allele is completely dominant over the recessive allele, what should be the phenotypic ratio of the progeny?   A. 3:1   B. 9:3:3:1   C. 4:4:4:4   D. 9:3:4
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