Alleles are: (A) true breeding homozygotes (B) different molecular forms of a gene (C) heterozygotes (D) different phenotypes

Options

A. true breeding homozygotes
B. different molecular forms of a gene
C. heterozygotes
D. diffeerent phenotypes

Answer

**Step-by-Step Text Solution:**

1. **Understanding Alleles:**
- Alleles are variations of a gene that occur at a specific locus on a chromosome. Each gene can have multiple forms, which are known as alleles.

2. **Identifying the Options:**
- (A) True breeding homozygotes: This refers to individuals that have two identical alleles for a trait, but it does not define what alleles are.
- (B) Different molecular forms of a gene: This accurately describes alleles as they represent variations of a single gene.
- (C) Heterozygotes: This term refers to individuals with two different alleles for a trait, which is not the definition of alleles.
- (D) Different phenotypes: While alleles can lead to different phenotypes, this option does not define alleles themselves.

3. **Correct Answer:**
- Based on the definitions, the correct answer is (B) Different molecular forms of a gene. Alleles are indeed different forms of a gene that can exist at the same locus on homologous chromosomes.

4. **Conclusion:**
- Therefore, the answer to the question "Alleles are:" is option (B) Different molecular forms of a gene.

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