Pure line breed refers to

Options

A. Heterozygosity only
B. Homozygosity only
C. Heterozygosity and linkage
D. Homozygosity and self-assortment

Answer

### Step-by-Step Solution:

1. **Understanding Pure Line Breeding**:
- Pure line breeding refers to a breeding method where individuals are genetically identical. This means that all the individuals in a pure line breed share the same genetic makeup.

2. **Identical Individuals**:
- In a pure line breed, all individuals produce the same phenotype, which means they exhibit the same observable characteristics. This consistency in traits is a hallmark of pure line breeding.

3. **Homozygosity**:
- The key characteristic of pure line breeds is that they are homozygous. This means that they possess two identical alleles for a particular gene. As a result, when these individuals reproduce, they consistently pass on the same alleles to their offspring.

4. **Offspring Production**:
- Since pure line breeds are homozygous, they produce offspring that are also homozygous for the same traits. This leads to a uniformity in the phenotype of the offspring, ensuring that the traits remain consistent across generations.

5. **Conclusion**:
- Therefore, the correct answer to the question "Pure line breed refers to" is **homozygosity only**. This aligns with the definition and characteristics of pure line breeding.

### Final Answer:
Pure line breed refers to **homozygosity only**.

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