When heterozygous tall plants are self - pollinated , then tall and dwarf plants are obtained . This explains

Options

A. Law of dominance
B. Law of segregation
C. division in spores
D. independent assortment

Answer

To solve the question, we need to understand the genetics behind the inheritance of traits in plants, particularly focusing on the height of the plants, which is controlled by a gene with two alleles: a dominant allele (T) for tallness and a recessive allele (t) for dwarfism.

### Step-by-Step Solution:

1. **Identify the Genotype of the Parent Plants:**
- The parent plants are heterozygous tall, meaning their genotype is Tt (one dominant allele and one recessive allele).

2. **Understand the Concept of Alleles:**
- Alleles are different forms of a gene. In this case, T (tall) is dominant, and t (dwarf) is recessive.

3. **Perform a Punnett Square Analysis:**
- To predict the offspring from the self-pollination of two heterozygous tall plants (Tt x Tt), we can use a Punnett square.
- The possible gametes from each parent are T and t.

| | T | t |
|-----|-----|-----|
| **T** | TT | Tt |
| **t** | Tt | tt |

4. **Analyze the Offspring Genotypes:**
- From the Punnett square, we can see the possible genotypes of the offspring:
- TT (homozygous tall) - 1 out of 4
- Tt (heterozygous tall) - 2 out of 4
- tt (homozygous dwarf) - 1 out of 4

5. **Determine the Phenotypic Ratio:**
- The phenotypic ratio of the offspring will be:
- Tall (TT and Tt): 3 out of 4
- Dwarf (tt): 1 out of 4
- This means that when heterozygous tall plants are self-pollinated, 75% of the offspring will be tall, and 25% will be dwarf.

6. **Explain the Result Using Genetic Laws:**
- The occurrence of dwarf plants among the offspring, despite both parents being tall, can be explained by the **Law of Segregation**. This law states that during gamete formation, the two alleles for a trait segregate from each other, so each gamete carries only one allele for each gene. Thus, even though the parents are tall, they carry the recessive allele (t), which can combine to produce dwarf offspring.

### Conclusion:
The explanation for obtaining both tall and dwarf plants from the self-pollination of heterozygous tall plants is due to the **Law of Segregation**.

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