Define. Dominance.

Answer

**Step-by-Step Solution:**

1. **Definition of Dominance**: Dominance refers to the phenomenon where one allele (variant of a gene) expresses its trait over another allele when both are present in an organism.

2. **Biological Context**: In biology, dominance is often discussed in the context of genetics, where certain traits are dominant over others. This means that if an organism has one dominant allele and one recessive allele, the dominant trait will be the one that is expressed.

3. **Example of Dominance**: A common example is the trait for plant height. If we consider two alleles for height:
- Tall (T) which is dominant
- Dwarf (t) which is recessive
In this case, a plant with the genotype TT (homozygous dominant) or Tt (heterozygous) will be tall, while only a plant with the genotype tt (homozygous recessive) will be dwarf.

4. **Representation of Alleles**: Dominant alleles are typically represented by capital letters (e.g., T for tall), while recessive alleles are represented by lowercase letters (e.g., t for dwarf).

5. **Conclusion**: Therefore, dominance is a key concept in understanding how traits are inherited and expressed in organisms, with dominant traits overshadowing recessive ones in heterozygous conditions.

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