Genotype refers to the genetic makeup of an individual for a particular trait. It's like the blueprint or code for a characteristic. Here's how homozygous and heterozygous genotypes differ:
Homozygous:
* Definition: An individual has two identical alleles for a specific trait.
* Example: Let's say the gene for eye color has two alleles: "B" (brown) and "b" (blue). A homozygous individual could have either:
* BB (homozygous dominant): Both alleles code for brown eyes.
* bb (homozygous recessive): Both alleles code for blue eyes.
Heterozygous:
* Definition: An individual has two different alleles for a specific trait.
* Example: Using the same eye color gene, a heterozygous individual would have:
* Bb: One allele codes for brown eyes, and the other codes for blue eyes.
Dominant and Recessive Alleles: The Key Players
* Dominant allele: An allele that expresses its trait even when paired with a recessive allele. It "masks" the effect of the recessive allele.
* Recessive allele: An allele that only expresses its trait when paired with another recessive allele.
How Dominant and Recessive Alleles Impact Heterozygotes
In a heterozygous individual (Bb), the dominant allele (B) will be expressed, determining the trait observed. In this case, the individual will have brown eyes even though they carry the recessive allele (b) for blue eyes.
Summary:
| Genotype | Alleles | Trait Expressed |
|---|---|---|
| Homozygous dominant | BB | Dominant trait |
| Homozygous recessive | bb | Recessive trait |
| Heterozygous | Bb | Dominant trait |
Key Takeaways:
* Homozygotes: Have two identical alleles, resulting in either the dominant or recessive trait being expressed.
* Heterozygotes: Have two different alleles, with the dominant trait being expressed due to its masking effect.
* Dominant alleles: Determine the trait expressed in heterozygotes.
* Recessive alleles: Only expressed when paired with another recessive allele in a homozygous recessive genotype.
Understanding the interplay between these concepts helps us decipher the genetic basis of traits and predict their inheritance patterns.
