Autosomal Inheritance: Videos & Practice Problems

Dig Deeper into Autosomal Inheritance

Autosomal inheritance refers to the transmission of genetic traits or disorders through non-sex chromosomes called autosomes.

Key Terminology

• Autosomes: Chromosomes that are not involved in determining the sex of an individual; humans have 22 pairs of autosomes.
• Alleles: Different versions of a gene that can exist at a specific locus on a chromosome.
• Dominant allele: An allele that expresses its trait even when only one copy is present (heterozygous or homozygous dominant).
• Recessive allele: An allele that only expresses its trait when two copies are present (homozygous recessive).
• Autosomal dominant disorder: A genetic disorder caused by a dominant allele on an autosome, where individuals with at least one dominant allele show the disorder.
• Autosomal recessive disorder: A genetic disorder caused by recessive alleles on autosomes, where only individuals homozygous recessive display the disorder.
• Homozygous dominant: Having two copies of the dominant allele for a gene.
• Homozygous recessive: Having two copies of the recessive allele for a gene.
• Heterozygous: Having one dominant and one recessive allele for a gene.
• Pedigree: A diagram that shows the inheritance pattern of a trait or disorder across generations in a family.
• Polydactyly: An example of an autosomal dominant disorder characterized by extra fingers or toes.
• Cystic fibrosis: An example of an autosomal recessive disorder affecting the respiratory and digestive systems.
• Genotype: The genetic makeup of an individual with respect to a particular gene.
• Phenotype: The observable traits or characteristics resulting from the genotype.

Real-World Applications

• Genetic counseling uses knowledge of autosomal inheritance patterns to assess the risk of passing on disorders like cystic fibrosis or polydactyly to offspring, helping families make informed reproductive decisions.
• Medical research on autosomal dominant and recessive disorders aids in developing gene therapies and personalized medicine approaches to treat or manage inherited diseases.
• Pedigree analysis is widely used in agriculture and animal breeding to track desirable traits and avoid genetic disorders, improving crop yields and livestock health.

Common Misconceptions

• “If a disorder is dominant, everyone with the allele will definitely have the disorder.” While dominant alleles usually cause the disorder to appear in every generation, some dominant disorders can show variable expressivity or incomplete penetrance, meaning not all individuals with the allele show symptoms.
• “Recessive disorders always skip generations.” Although autosomal recessive disorders often appear to skip generations because carriers (heterozygotes) do not show symptoms, the disorder can appear in any generation if two carriers have affected offspring.
• “Only males can inherit sex-linked disorders.” Autosomal inheritance involves non-sex chromosomes, so both males and females can inherit autosomal dominant or recessive disorders equally.
• “Having one dominant allele means you are a carrier.” In autosomal dominant disorders, having one dominant allele means you usually express the disorder, unlike recessive disorders where carriers have one recessive allele but do not show symptoms.