Genetic Inheritance Patterns - Lecture 24

Genetic Inheritance Patterns - Lecture 24

• The lecture covers patterns of genetic inheritance, specifically autosomal dominant inheritance.
• Pedigrees are used to trace the inheritance of traits across generations.
• Pedigree analysis involves understanding symbols and connecting them to show inheritance relationships.
• Autosomal dominant inheritance means a trait expressed even with only one copy of the disease gene (heterozygote).

Complicating Factors in Autosomal Dominant Inheritance

• Non-Penetrance: An individual with a disease-causing variant may not show the associated trait. The trait may "skip" generations.
• New Mutation: A new mutation in the egg or sperm cell of a parent creates a trait not seen in prior family history.
• Adult-Onset Conditions: Some conditions manifest only after adulthood or later in life.
• Consanguinity: The presence of shared ancestors in parents increases the risk of genetic abnormalities, especially in autosomal recessive conditions.
• Interaction: Other factors that could play a role in gene expression.

Sex-Limited/Sex-Influenced Traits

• Autosomal traits are influenced by the sex of the individual.
• In males, one recessive allele is enough to show the trait; in females, two are required for the same trait.
• Gene expression may differ due to sex hormones or other factors.

New Mutations in Autosomal Dominant Inheritance

• A new mutation that causes the disease may be present in one parent, creating an affected individual.
• The recurrence risk in unaffected parents is low.
• There may be an association with advanced paternal age in some disorders.

Late-Onset Traits

• Some genetic disorders appear much later in life. Huntington's disease is an example.
• These are distinguished from other diseases that often appear in childhood or early adulthood.

Variable Expressivity

• The severity of the trait may vary among individuals with the same genotype.
• Neurofibromatosis, for example, presents with differing degrees of severity.

Locus Heterogeneity

• Different gene locations can lead to similar traits (phenocopies) despite the genes being different.

Pleiotropy

• One single gene can affect multiple, seemingly unrelated physical traits. This means the gene has multiple effects.
• Marfan syndrome is an example of pleiotropy.

This quiz explores autosomal dominant inheritance and the use of pedigrees to trace genetic traits across generations. It delves into complicating factors such as non-penetrance, new mutations, and their impact on inheritance. Test your knowledge on these essential concepts in genetics.