Homozygous purelines in cattle can be obtained by

Options

A. mating of related individuals of same breed
B. mating of unrealted individuals of same breed
C. mating of individuals of different breed
D. matting of individuals of different species

Answer

### Step-by-Step Solution:

1. **Understanding Homozygous Pure Lines**:
- Homozygous pure lines refer to individuals that are genetically uniform, meaning they have identical alleles for a particular trait. This results in offspring that are also homozygous for those traits.

2. **Identifying Mating Types**:
- The question provides four options regarding how homozygous pure lines can be obtained:
1. Mating of related individuals of the same breed.
2. Mating of unrelated individuals of the same breed.
3. Mating of individuals of different breeds.
4. Mating of individuals of different species.

3. **Analyzing Each Option**:
- **Option 1**: Mating of related individuals of the same breed.
- This method promotes homozygosity because related individuals share similar genetic backgrounds, leading to offspring that are more likely to inherit the same alleles.
- **Option 2**: Mating of unrelated individuals of the same breed.
- This would introduce genetic diversity and is less likely to produce homozygous offspring.
- **Option 3**: Mating of individuals of different breeds.
- This would also introduce genetic diversity and is not conducive to creating homozygous pure lines.
- **Option 4**: Mating of individuals of different species.
- This is not possible in most cases due to reproductive barriers and would not lead to homozygous pure lines.

4. **Conclusion**:
- The most effective method for obtaining homozygous pure lines is through the mating of related individuals of the same breed. This method ensures that the offspring will inherit similar genetic traits, leading to homozygosity.

### Final Answer:
Homozygous pure lines in cattle can be obtained by the mating of related individuals of the same breed.

---