Mendel's third law of independent assortment can be demonstrated by

Options

A. Test cross
B. Back cross
C. Monohybrid cross
D. Dihybrid cross

Answer

To demonstrate Mendel's third law of independent assortment, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Mendel's Laws**: Mendel proposed three laws of inheritance based on his experiments with pea plants. The third law, known as the Law of Independent Assortment, states that alleles for different traits segregate independently of one another during gamete formation.

**Hint**: Recall the three laws of inheritance proposed by Mendel and focus on the one that deals with the segregation of different traits.

2. **Setting Up the Experiment**: To demonstrate this law, we can perform a dihybrid cross. This involves crossing two organisms that differ in two traits. For example, we can cross a plant with round yellow seeds (genotype RRYY) with a plant that has wrinkled green seeds (genotype rryy).

**Hint**: Think about what traits you want to observe and how many traits are involved in a dihybrid cross.

3. **F1 Generation**: The offspring of this cross (F1 generation) will all be heterozygous for both traits (RrYy). Since round (R) and yellow (Y) are dominant traits, all F1 plants will exhibit the dominant phenotype: round and yellow seeds.

**Hint**: Remember that in a dihybrid cross, the F1 generation will show the dominant traits of both parents.

4. **F2 Generation**: Next, we self-cross the F1 generation (RrYy x RrYy). In the F2 generation, we will observe a variety of phenotypes. The expected phenotypic ratio will be 9:3:3:1, which includes:
- 9 round yellow
- 3 round green
- 3 wrinkled yellow
- 1 wrinkled green

**Hint**: Calculate the expected ratios for the F2 generation based on the combinations of alleles.

5. **Analyzing the Results**: The presence of phenotypes that are combinations of the traits (like round green and wrinkled yellow) indicates that the traits assort independently. This means that the inheritance of one trait does not affect the inheritance of the other trait.

**Hint**: Look for the combinations that do not resemble either parent to confirm independent assortment.

6. **Conclusion**: From the results of the dihybrid cross, we conclude that the traits for seed shape and seed color are inherited independently of each other, thus demonstrating Mendel's Law of Independent Assortment.

**Hint**: Summarize the findings and relate them back to the law to reinforce the concept.

### Summary:
To demonstrate Mendel's third law of independent assortment, perform a dihybrid cross between two plants differing in two traits, analyze the F2 generation, and observe the independent assortment of traits through the phenotypic ratios.