what is the difference between heterozygous and homozygous?
## What is the difference between heterozygous and homozygous?
Answer:
In genetics, heterozygous and homozygous are terms used to describe the composition of alleles (alternative forms of a gene) in an organism’s genotype:
1. Definition of Alleles
- Alleles are different versions of the same gene. For example, a gene determining flower color might have one allele that produces purple flowers and another that produces white flowers.
2. Homozygous
- Homozygous means an organism has two identical alleles for a specific gene.
- These alleles can both be dominant (AA) or both be recessive (aa).
- Homozygous organisms will consistently show the trait determined by those identical alleles.
3. Heterozygous
- Heterozygous means an organism has two different alleles for a specific gene (e.g., Aa).
- One allele may be dominant and the other recessive, often resulting in the dominant phenotype being expressed.
- Heterozygosity contributes to genetic variation within a population.
4. Example
- If a plant’s gene for flower color has two alleles (A = red color, a = white color):
- AA (homozygous dominant) → Red flowers
- aa (homozygous recessive) → White flowers
- Aa (heterozygous) → Red flowers (dominant allele “A” is expressed)
Key Points to Remember
- Homozygous: Identical alleles (AA or aa).
- Heterozygous: Different alleles (Aa).
- Phenotypic Expression: A heterozygous individual often shows the dominant trait.
- Genetic Variation: Heterozygosity increases variation in a population, while homozygosity tends to stabilize specific traits.
| Term | Allele Composition | Phenotype Expression | Example |
|---|---|---|---|
| Homozygous | Two identical alleles (AA, aa) | Consistent expression of the same trait | AA = Red, aa = White |
| Heterozygous | Two different alleles (Aa) | Often shows the dominant allele’s trait (depends on dominance) | Aa = Red |