Ch. 14 - Mendel and the Gene

Freeman - Biological Science 7th Edition

Freeman7th EditionBiological ScienceISBN: 9783584863285Not the one you use?Change textbook

Freeman 7th Edition

Ch. 14 - Mendel and the Gene

Problem 8

Chapter 14, Problem 8

In garden peas, yellow seeds (Y) are dominant to green seeds (y), and inflated pods (I) are dominant to constricted pods (i). Suppose you have crossed YYII parents with yyii parents. Draw the F2 Punnett square. Based on this Punnett square, predict the expected phenotype(s) in the F2 generation and the expected frequency of each phenotype.

Verified step by step guidance

Step 1: Determine the genotypes of the parent generation. The first parent is YYII (homozygous dominant for both traits) and the second parent is yyii (homozygous recessive for both traits).

Step 2: Perform a cross between the F1 generation. Since all F1 offspring from the initial cross will be YyIi (heterozygous for both traits), you will cross YyIi x YyIi to obtain the F2 generation.

Step 3: Set up a Punnett square for the F2 generation. Since each parent can produce four different types of gametes (YI, Yi, yI, yi), create a 4x4 Punnett square to account for all possible combinations of these gametes.

Step 4: Fill in the Punnett square with the genotypes resulting from each combination of gametes. This will help you visualize the distribution of genotypes in the F2 generation.

Step 5: Determine the phenotypes corresponding to each genotype and calculate their frequencies. Remember that yellow seeds (Y) are dominant over green seeds (y) and inflated pods (I) are dominant over constricted pods (i). Use the genotypic ratios from the Punnett square to predict the phenotypic ratios.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Mendelian Genetics

Mendelian genetics is the study of how traits are inherited through generations based on the principles established by Gregor Mendel. It involves understanding dominant and recessive alleles, where dominant alleles mask the expression of recessive ones. In this case, yellow seeds (Y) and inflated pods (I) are dominant traits, while green seeds (y) and constricted pods (i) are recessive.

Punnett Square

A Punnett square is a diagram used to predict the genotypic and phenotypic outcomes of a genetic cross. It organizes the possible combinations of alleles from each parent, allowing for the visualization of inheritance patterns. In this scenario, the Punnett square will help determine the expected phenotypes of the F2 generation from the cross of YYII and yyii parents.

Phenotypic Ratios

Phenotypic ratios represent the relative frequencies of different phenotypes resulting from a genetic cross. In the F2 generation, the expected phenotypes can be calculated based on the combinations of alleles from the Punnett square. For example, if the F1 generation is heterozygous, the F2 generation will exhibit a specific ratio of dominant to recessive traits, which can be expressed as a fraction or percentage.

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Genotypic vs. Phenotypic Ratio

Related Practice

Textbook Question

In flies, small wings are recessive to normal wings. If a cross between two flies produces 8 small-wing offspring and 28 normal-wing offspring, what are the most likely genotypes of the parents? (Use S to represent the normal-wing allele and s to represent the short-wing allele.)

In garden peas, yellow seeds (Y) are dominant to green seeds (y), and inflated pods (I) are dominant to constricted pods (i). Suppose you have crossed YYII parents with yyii parents. Draw the F1 Punnett square and predict the expected F1 phenotype(s).

In garden peas, yellow seeds (Y) are dominant to green seeds (y), and inflated pods (I) are dominant to constricted pods (i). Suppose you have crossed YYII parents with yyii parents. List the genotype(s) of gametes produced by F1 individuals.

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Textbook Question

In garden peas, yellow seeds (Y) are dominant to green seeds (y), and inflated pods (I) are dominant to constricted pods (i). Suppose you have crossed YYII parents with yyii parents. Draw the F2 Punnett square. Based on this Punnett square, predict the expected phenotype(s) in the F2 generation and the expected frequency of each phenotype.

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