Holandric genes are present on
(a) X-chromosomes
(b) Y-chromosomes
(c) Sex-chromosomes as well as autosomes
(d) Autosomes

Options

A. X-chromosomes
B. Y-chromosomes
C. Sex-chromosomes as well as autosomes
D. Autosomes

Answer

To solve the question regarding holandric genes, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Holandric Genes**:
- Holandric genes are defined as genes that are located exclusively on the Y chromosome. This means that these genes are inherited only through the male lineage.

2. **Identifying Chromosome Types**:
- In humans, there are two types of sex chromosomes: X and Y. The X chromosome carries a variety of genes, while the Y chromosome is much smaller and carries genes that are primarily related to male sex determination and spermatogenesis.

3. **Analyzing the Options**:
- (a) X-chromosomes: This option is incorrect because holandric genes are not found on the X chromosome.
- (b) Y-chromosomes: This option is correct as holandric genes are specifically located on the Y chromosome.
- (c) Sex-chromosomes as well as autosomes: This option is incorrect because holandric genes are not found on autosomes or the X chromosome.
- (d) Autosomes: This option is incorrect as holandric genes are not located on autosomes.

4. **Conclusion**:
- Based on the definitions and analysis of the options, the correct answer is (b) Y-chromosomes.

### Final Answer:
(b) Y-chromosomes

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