Dominant Genes:
* Definition: A dominant gene is one that expresses its trait even if only one copy of the gene is present. It essentially "masks" the effect of the recessive gene.
* Symbol: Represented by an uppercase letter (e.g., "B" for brown eyes).
* Example: If a person inherits one gene for brown eyes (B) and one gene for blue eyes (b), they will have brown eyes because the brown eye gene (B) is dominant.
Recessive Genes:
* Definition: A recessive gene only expresses its trait if two copies of the gene are present. It needs to be paired with another recessive gene for the trait to show up.
* Symbol: Represented by a lowercase letter (e.g., "b" for blue eyes).
* Example: A person will only have blue eyes if they inherit two blue eye genes (bb). If they inherit one brown eye gene (B) and one blue eye gene (b), they will have brown eyes.
Key Points:
* Heterozygous vs. Homozygous:
* Heterozygous: An individual with one dominant and one recessive allele (e.g., Bb for brown eyes).
* Homozygous: An individual with two of the same alleles (e.g., BB for brown eyes or bb for blue eyes).
* Not all traits are simple: Many traits are influenced by multiple genes (polygenic inheritance) or by interactions between genes and the environment.
* Not always about "better": Dominant genes aren't necessarily better or more desirable. For example, Huntington's disease is caused by a dominant gene, while cystic fibrosis is caused by a recessive gene.
Example:
Imagine eye color:
* Brown eyes: Dominant (B)
* Blue eyes: Recessive (b)
Possible combinations:
* BB: Brown eyes (homozygous dominant)
* Bb: Brown eyes (heterozygous)
* bb: Blue eyes (homozygous recessive)
Let me know if you'd like more examples or have any other questions about genetics!
