Haploids are preferred over diploids for mutation studies because in haploids:
(a) Recessive mutation express immediately
(b) Dominant mutations express immediately
(c) Mutation are readily induced
(d) Tissue culture is easy

Options

A. Recessive mutation express immediately
B. Dominant mutations express immediately
C. Mutation are readily induced
D. Tissue culture is easy.

Answer

To solve the question regarding why haploids are preferred over diploids for mutation studies, we can analyze each option provided:

1. **Understanding Haploids and Diploids**:
- Haploids have only one set of chromosomes (n), while diploids have two sets (2n). This difference is crucial in how mutations are expressed.

2. **Analyzing the Options**:
- **Option (a)**: Recessive mutations express immediately.
- In haploids, since there is only one allele for each gene, any recessive mutation will be expressed immediately. There is no dominant allele to mask the effect of the recessive mutation.
- **Option (b)**: Dominant mutations express immediately.
- While dominant mutations do express immediately in both haploids and diploids, the question focuses on the preference for haploids in mutation studies. This option is not the primary reason for choosing haploids.
- **Option (c)**: Mutations are readily induced.
- While mutations can be induced in both haploids and diploids, this does not specifically justify the preference for haploids in mutation studies.
- **Option (d)**: Tissue culture is easy.
- Tissue culture can be complex and is not a reason for preferring haploids over diploids.

3. **Conclusion**:
- The most compelling reason for preferring haploids for mutation studies is that recessive mutations express immediately due to the absence of a second allele that could mask their expression. Therefore, the correct answer is **(a) Recessive mutations express immediately**.

### Final Answer:
**(a) Recessive mutations express immediately.**