A pea plant heterozygous for inflated pods (Ii) is crossed with a plant homozygous for constricted pods (ii). Draw a Punnett square for this cross to predict genotypic and phenotypic ratios. Assume that pollen comes from the ii plant.

Verified step by step guidance

1. Step 1: Understand the genetic makeup of the two parent plants. The heterozygous pea plant has the genotype Ii, where 'I' represents the dominant allele for inflated pods and 'i' represents the recessive allele for constricted pods. The homozygous pea plant has the genotype ii, with both alleles being recessive for constricted pods.
2. Step 2: Set up the Punnett square. A Punnett square is a grid used to predict the genotypes and phenotypes of offspring from a genetic cross. Write the alleles of the ii plant (pollen donor) along the top of the square and the alleles of the Ii plant (egg donor) along the side of the square.
3. Step 3: Fill in the Punnett square by combining the alleles from the top and side of the grid. Each box in the square represents a possible genotype for the offspring. For example, combine the 'I' allele from the Ii plant with the 'i' allele from the ii plant to form one genotype.
4. Step 4: Determine the genotypic ratio by counting the number of each genotype in the Punnett square. The possible genotypes are Ii (heterozygous for inflated pods) and ii (homozygous for constricted pods).
5. Step 5: Determine the phenotypic ratio by analyzing the traits expressed by each genotype. Since 'I' is dominant, any offspring with the genotype Ii will have inflated pods, while offspring with the genotype ii will have constricted pods.

Key Concepts

Punnett Square

A Punnett square is a diagram used to predict the outcome of a genetic cross by displaying the possible combinations of alleles from the parents. Each cell in the square represents a potential genotype of the offspring, allowing for easy visualization of genetic ratios. In this case, it will help determine the genotypic and phenotypic ratios of the offspring from the cross between a heterozygous and a homozygous plant.

Genotype and Phenotype

Genotype refers to the genetic makeup of an organism, specifically the alleles it possesses for a particular trait. Phenotype, on the other hand, is the observable expression of that genotype, influenced by both genetic and environmental factors. In the context of the pea plant cross, understanding the difference between these terms is crucial for interpreting the results of the Punnett square.

Mendelian Inheritance

Mendelian inheritance is the set of principles that explain how traits are passed from parents to offspring, based on the work of Gregor Mendel. It includes concepts such as dominance, segregation, and independent assortment. In this scenario, the dominant allele for inflated pods (I) will mask the recessive allele for constricted pods (i), which is essential for predicting the phenotypic ratios in the offspring.