Here's a breakdown:
* Alleles: Different versions of a gene.
* Recessive Allele: An allele that only expresses its trait when two copies are present.
* Dominant Allele: An allele that expresses its trait even when only one copy is present.
Example:
Let's say the gene for eye color has two alleles:
* B: Brown eye allele (dominant)
* b: Blue eye allele (recessive)
Possible Genotypes and Phenotypes:
* BB: Brown eyes (dominant)
* Bb: Brown eyes (dominant)
* bb: Blue eyes (recessive)
In the case of blue eyes, an individual must inherit a "b" allele from both parents (genotype "bb") to express the recessive trait.
Why you see it:
* No dominant allele: When there's no dominant allele to "mask" the recessive one, the recessive trait is expressed.
* Two recessive alleles: The recessive allele needs to be present twice for its trait to be visible.
Important Notes:
* Heterozygotes: Individuals with one dominant and one recessive allele (Bb) carry the recessive allele but don't express it. They are called carriers.
* Not always visible: Some recessive traits might not be immediately noticeable, like genetic predispositions for certain diseases.
Let me know if you'd like to explore specific examples or have further questions!
