A diploid with only one allele (e.g., man is for XY chromosomes) is known as

Options

A. homozygous
B. hemizygous
C. heterozygous
D. none of these

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the term used to describe a diploid organism that has only one allele for a specific trait. The example given is a man with XY chromosomes.

2. **Identifying the Options**: The question provides four options, three of which are technical terms related to genetic conditions: homozygous, hemizygous, and heterozygous.

3. **Defining Homozygous Condition**:
- In a homozygous condition, an individual has two identical alleles for a trait. For example, in humans, a female with XX chromosomes is homozygous for the X chromosome.

4. **Defining Heterozygous Condition**:
- In a heterozygous condition, an individual has two different alleles for a trait. For example, in pea plants, a genotype of Tt (where T is dominant and t is recessive) represents a heterozygous condition.

5. **Defining Hemizygous Condition**:
- The term hemizygous refers to a condition where an individual has only one allele for a gene instead of the usual two. This is common in males with XY chromosomes, where they have one X chromosome and one Y chromosome. Thus, they are hemizygous for the genes located on the X chromosome.

6. **Conclusion**: Based on the definitions, the correct term for a diploid organism that has only one allele (like a man with XY chromosomes) is **hemizygous**.

**Final Answer**: Hemizygous condition.

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