Any gene that produces an effect in the heterozygous conditon is called dominant.

Answer

### Step-by-Step Solution:

1. **Understanding Dominance**: The statement defines a dominant gene as one that expresses its effect in a heterozygous condition. This means that if an organism has two different alleles for a trait (one dominant and one recessive), the dominant allele will determine the phenotype.

**Hint**: Recall the definitions of dominant and recessive alleles.

2. **Mendel's Contribution**: The concept of dominance is rooted in the work of Gregor Mendel, who is known as the father of genetics. Mendel's experiments with pea plants led to the formulation of the laws of inheritance, including the law of dominance.

**Hint**: Think about Mendel's experiments with traits in pea plants.

3. **Alleles and Genotypes**: According to Mendel, each trait is controlled by a gene that exists in pairs (alleles). For example, a gene for plant height can have a dominant allele (T) for tallness and a recessive allele (t) for dwarfism.

**Hint**: Remember the terms allele, genotype, and phenotype.

4. **Examples of Genotypes**: There are three possible genotypes for a trait controlled by two alleles:
- Homozygous dominant (TT) - phenotype is tall.
- Homozygous recessive (tt) - phenotype is dwarf.
- Heterozygous (Tt) - phenotype is tall due to the presence of the dominant allele.

**Hint**: Consider how different combinations of alleles affect the phenotype.

5. **Expression of Phenotype**: In the case of the heterozygous genotype (Tt), the dominant allele (T) masks the effect of the recessive allele (t). Therefore, the phenotype will reflect the dominant trait.

**Hint**: Think about how the dominant allele suppresses the recessive one.

6. **Conclusion**: The statement is accurate; a gene that produces an effect in the heterozygous condition is indeed called a dominant gene. The recessive gene will only express itself in a homozygous condition (tt).

**Hint**: Summarize the key points about dominant and recessive alleles.