Introduction
Autosomal dominant traits are genetic characteristics that are passed from one generation to the next through a dominant allele located on one of the autosomes (non-sex chromosomes). These traits are easily observable in families because they appear in every generation. Understanding their features is essential for predicting inheritance patterns and diagnosing genetic disorders.
Key Features of Autosomal Dominant Traits
1. Expression in Heterozygous State
Only one copy of the dominant allele is sufficient to express the trait. This means individuals with genotype Aa (one dominant, one recessive) will show the dominant phenotype.
2. Equal Transmission to Both Sexes
Since the gene is on an autosome, both males and females have an equal chance of inheriting and passing on the trait.
3. Vertical Pattern of Inheritance
The trait typically appears in every generation. Affected individuals usually have at least one affected parent.
4. 50% Transmission Risk
If one parent is affected (heterozygous) and the other is unaffected, there is a 50% chance the child will inherit the condition.
5. Unaffected Individuals Do Not Pass on the Trait
People who do not have the dominant allele (aa) will not develop the trait and will not pass it to their offspring.
Examples of Autosomal Dominant Disorders
- Huntington’s disease
- Achondroplasia (a form of dwarfism)
- Marfan syndrome
- Polydactyly (extra fingers or toes)
Conclusion
Autosomal dominant traits are easily traceable through family trees because of their consistent appearance across generations. Recognizing these features helps in genetic counseling, risk assessment, and early diagnosis of inherited conditions.