Genes are segments of DNA that influence traits and biological functions. Inheritance patterns of genes can be classified as dominant or recessive, determining how traits are passed down and expressed.
Dominant genes
Dominant genes are genes that will express their traits even if only one copy is inherited (from one parent). A dominant gene masks the effect of a recessive gene if both are present.
Characteristics
Expression in heterozygous individuals: A dominant gene shows its trait even when paired with a recessive gene.
Examples: Brown eyes, widow’s peak and the ability to roll the tongue are examples of dominant traits.
Recessive genes
Recessive genes only express their traits when two copies of the gene are inherited, one from each parent. If a dominant gene is present, it will mask the recessive gene’s trait.
Characteristics
Expression in homozygous individuals: A recessive gene expresses its trait only when two copies are inherited (one from each parent).
Examples: Blue eyes, cystic fibrosis and sickle cell anemia are examples of traits controlled by recessive genes.
Key differences between dominant and recessive genes
| Feature | Dominant genes | Recessive genes |
|---|---|---|
| Number of copies for expression | Only one copy needed for the trait to appear. | Two copies needed for the trait to show up. |
| Expression in individuals | Expressed in heterozygous (one dominant, one recessive allele) and homozygous dominant (two dominant alleles) individuals. | Only expressed in homozygous recessive individuals (two recessive alleles). |
| Visibility of traits | Traits are usually visible (e.g., brown eyes, tongue rolling). | Traits are often hidden unless both alleles are recessive (e.g., blue eyes, cystic fibrosis). |
| Inheritance patterns | 50% chance of inheritance if one parent carries the dominant gene. | Both parents must pass on a recessive allele for a 25% chance of inheritance. |
| Impact on genetic disorders | Disorders can appear even if only one parent carries the gene (e.g., Huntington’s disease). | Disorders require both parents to carry the gene (e.g., cystic fibrosis). |
Both dominant and recessive genes play a significant role in determining traits and overall health. Their interaction can influence longevity by impacting disease resistance and aging processes. Understanding how these genes work is key to understanding genetic inheritance and its effect on lifespan.
