Autosomal Disorder Pedigree Analysis
The webpage is under continuous improvement. We welcome your feedback and suggestions.
Autosomal Disorder Pedigree Analysis
Autosomal disorders are genetic conditions that are inherited through the autosomes, which are the non-sex chromosomes (chromosomes 1-22 in humans).
When analyzing pedigrees to determine the inheritance pattern of an autosomal disorder, several key rules and characteristics can help identify whether a disorder is autosomal dominant or autosomal recessive. Below is a guide to understanding and identifying these patterns in pedigree analysis.
Autosomal Dominant Disorder
Understanding with Example:
A parent with an autosomal dominant disorder (e.g., Huntington's disease) has a 50% chance of passing the mutated gene to each child.
Pedigree Indicators:
At least one affected parent.
Does not skip generations (vertical pattern).
Roughly equal numbers of affected males and females.
Characteristics:
Inheritance from Either Parent: The disorder can be inherited from either the mother or the father.
Every Generation: The disorder usually appears in every generation. An affected individual has at least one affected parent.
Both Genders Equally Affected: Males and females are equally likely to be affected.
No Carriers: There are no carriers; if an individual has the allele, they express the disorder.
50% Probability: An affected individual has a 50% chance of passing the disorder to their offspring, regardless of the partner's genotype.
Autosomal Recessive Disorder
Understanding with Example:
Two carriers of an autosomal recessive disorder (e.g., cystic fibrosis) have a 25% chance of having an affected child.
Pedigree Indicators:
May skip generations (horizontal pattern).
Affected individuals often have unaffected parents who are carriers.
Affected individuals may have affected siblings but unaffected parents.
Characteristics:
Both Parents as Carriers: The disorder is often seen when both parents are carriers (heterozygous).
Skipping Generations: The disorder may skip generations, appearing only when two carriers have children.
Both Genders Equally Affected: Males and females are equally likely to be affected.
Carriers Present: Individuals who carry one copy of the mutated gene do not exhibit symptoms.
25% Probability: Two carrier parents have a 25% chance of having an affected child, a 50% chance of having a carrier child, and a 25% chance of having a non-carrier child.