Homozygous:
* Definition: An individual is homozygous for a particular gene when they have two identical alleles for that gene.
* Example: If an individual has two copies of the dominant allele "B" for brown eyes, they are homozygous dominant (BB). Similarly, if they have two copies of the recessive allele "b" for blue eyes, they are homozygous recessive (bb).
* Characteristics:
* Predictable phenotype: Since both alleles are the same, the trait they express is predictable.
* No variation in offspring: Offspring inherit the same allele from both parents, leading to no variation in that specific trait.
Heterozygous:
* Definition: An individual is heterozygous for a particular gene when they have two different alleles for that gene.
* Example: If an individual has one copy of the dominant allele "B" for brown eyes and one copy of the recessive allele "b" for blue eyes, they are heterozygous (Bb).
* Characteristics:
* Dominant allele expression: The phenotype is determined by the dominant allele (in the example above, brown eyes would be expressed).
* Possible variation in offspring: Offspring inherit different alleles from each parent, leading to potential variation in that specific trait.
Key Differences:
| Feature | Homozygous | Heterozygous |
|---|---|---|
| Allele combination | Two identical alleles | Two different alleles |
| Phenotype | Predictable | Determined by dominant allele |
| Offspring variation | No variation | Potential variation |
In simple terms:
Think of it like having two socks:
* Homozygous: You have two identical socks (both blue or both red).
* Heterozygous: You have two different socks (one blue and one red).
The dominant allele is like the louder sock, while the recessive allele is like the quieter sock. In a heterozygous situation, the louder sock's color is the one you see.
