* Recessive traits require two copies of the recessive allele: For a recessive trait to be expressed, an individual needs to inherit two copies of the recessive allele (one from each parent).
* Dominant alleles mask recessive alleles: If an individual inherits one dominant allele and one recessive allele, the dominant allele will be expressed, and the recessive trait will not be visible.
Example:
* Brown eyes (B) are dominant to blue eyes (b).
* A person with the genotype BB will have brown eyes.
* A person with the genotype Bb will also have brown eyes, even though they carry the blue eye allele.
* Only a person with the genotype bb will have blue eyes.
Therefore, a recessive trait will only be shown in an offspring if both parents carry the recessive allele and pass it on.
In other words:
* If both parents are carriers (Bb) of the recessive trait, there is a 25% chance of their child inheriting two recessive alleles (bb) and displaying the recessive trait.
* If one parent is a carrier (Bb) and the other has two dominant alleles (BB), there is no chance of their child displaying the recessive trait.
It's important to note:
* Not all traits are determined by simple dominant/recessive inheritance patterns. Many traits are influenced by multiple genes (polygenic traits) or by interactions between genes and the environment.
* Carrier testing can help individuals determine if they carry a recessive allele for a specific trait. This information can be useful for family planning.
