Two pea plants heterozygous for the characters of pod color and pod shape are crossed. Draw a Punnett square to determine the phenotypic ratios of the offspring.

Verified step by step guidance

1. Step 1: Identify the genotypes of the parent plants. Since both plants are heterozygous for pod color and pod shape, their genotypes are 'GgSs', where 'G' represents the dominant allele for green pod color, 'g' represents the recessive allele for yellow pod color, 'S' represents the dominant allele for smooth pod shape, and 's' represents the recessive allele for constricted pod shape.
2. Step 2: Determine the possible gametes each parent can produce. Use the FOIL (First, Outer, Inner, Last) method to combine the alleles for each trait. For a 'GgSs' parent, the possible gametes are 'GS', 'Gs', 'gS', and 'gs'.
3. Step 3: Set up a 4x4 Punnett square. Label the rows with the gametes from one parent ('GS', 'Gs', 'gS', 'gs') and the columns with the gametes from the other parent ('GS', 'Gs', 'gS', 'gs').
4. Step 4: Fill in the Punnett square by combining the alleles from the rows and columns. For example, the combination of 'GS' (row) and 'Gs' (column) would result in the genotype 'GGSs'. Repeat this process for all 16 squares in the Punnett square.
5. Step 5: Analyze the genotypes in the Punnett square to determine the phenotypic ratios. Group the offspring based on their phenotypes (e.g., green smooth, green constricted, yellow smooth, yellow constricted) by considering the dominance of the alleles ('G' is dominant over 'g', and 'S' is dominant over 's'). Count the number of each phenotype to determine the ratios.

Key Concepts

Punnett Square

A Punnett square is a diagram used to predict the genotypes and phenotypes of offspring from a genetic cross. It organizes the possible combinations of alleles from each parent, allowing for a visual representation of inheritance patterns. In this case, it will help determine the ratios of different phenotypes resulting from the cross of two heterozygous pea plants.

Heterozygous

Heterozygous refers to an organism that has two different alleles for a particular gene, one inherited from each parent. In the context of the pea plants, being heterozygous for pod color and pod shape means that each plant carries one dominant and one recessive allele for these traits. This genetic variation is crucial for understanding the potential outcomes in the offspring.

Phenotypic Ratio

The phenotypic ratio is the relative frequency of different phenotypes in the offspring resulting from a genetic cross. It is calculated by analyzing the outcomes from the Punnett square, which shows how traits are expressed based on the combinations of alleles. Understanding phenotypic ratios helps in predicting the likelihood of certain traits appearing in the next generation.