An organism with two identical alleles for a given trait is:

Options

A. dominant
B. hybrid
C. heterozygous
D. homozygous

Explanation

To solve the question "An organism with two identical alleles for a given trait is:", we can follow these steps:

### Step 1: Understand the terms related to alleles
- Alleles are different forms of a gene that can exist at a specific locus on a chromosome.
- An organism can have either two identical alleles or two different alleles for a trait.

### Step 2: Define homozygous
- When an organism has two identical alleles for a trait, it is referred to as "homozygous." For example, if an organism has two dominant alleles (AA) or two recessive alleles (aa), it is homozygous.

### Step 3: Define heterozygous
- In contrast, if an organism has two different alleles for a trait, it is called "heterozygous." For example, an organism with one dominant allele and one recessive allele (Aa) is heterozygous.

### Step 4: Clarify dominant and recessive
- The term "dominant" refers to an allele that can mask the effect of another allele. For example, if T is dominant over t, then TT and Tt will express the dominant trait, while tt will express the recessive trait.

### Step 5: Conclusion
- Based on the definitions and understanding of the terms, the correct answer to the question is that an organism with two identical alleles for a given trait is **homozygous**.

### Final Answer:
An organism with two identical alleles for a given trait is **homozygous**.

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