Mendel crossed peas having round seeds and yellow cotyledons (seed leaves) with peas having wrinkled seeds and green cotyledons. All the F₁ plants had round seeds with yellow cotyledons. Diagram this cross through the F₂ generation, using both the Punnett square and forked-line, or branch diagram, methods.

Verified step by step guidance

1. <insert step 1: Identify the genotypes of the parent plants. Round seeds (R) are dominant over wrinkled seeds (r), and yellow cotyledons (Y) are dominant over green cotyledons (y). The parent plants are homozygous: RRYY (round, yellow) and rryy (wrinkled, green).>
2. <insert step 2: Determine the genotype of the F₁ generation. Since all F₁ plants have round seeds and yellow cotyledons, they must be heterozygous for both traits: RrYy.>
3. <insert step 3: Set up a Punnett square for the F₂ generation. The F₁ plants (RrYy) will produce gametes with the following combinations: RY, Ry, rY, ry. Create a 4x4 Punnett square to determine the genotypes of the F₂ generation.>
4. <insert step 4: Use the forked-line method to determine the phenotypic ratios. Start with one trait (e.g., seed shape) and determine the probability of each phenotype, then branch out to the second trait (e.g., cotyledon color) to find the combined probabilities.>
5. <insert step 5: Analyze the results from both methods to determine the phenotypic ratio of the F₂ generation. The expected phenotypic ratio for a dihybrid cross is 9:3:3:1, where 9 have both dominant traits, 3 have one dominant and one recessive trait, 3 have the other dominant and recessive trait, and 1 has both recessive traits.>

Key Concepts

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 traits mask the expression of recessive ones. In this case, round seeds and yellow cotyledons are dominant traits, while wrinkled seeds and green cotyledons are recessive.

Punnett Square

A Punnett square is a diagram used to predict the genotypes 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 scenario, the Punnett square will help illustrate the expected ratios of round versus wrinkled seeds and yellow versus green cotyledons in the F₂ generation.

Forked-Line (Branch Diagram)

The forked-line or branch diagram is another method for visualizing genetic crosses, particularly useful for multiple traits. It systematically branches out the possible combinations of alleles, showing how each trait segregates independently. This method complements the Punnett square by providing a clear view of the inheritance of multiple traits, such as seed shape and cotyledon color in this cross.