Complex Multigenic
Complex/multigenic disorders — many genes interacting with environment (e.g., diabetes, hypertension, most common adult diseases)
What our notes say
- Complex/multigenic disorders — many genes interacting with environment (e.g., diabetes, hypertension, most common adult diseases) (Clinical Genetics: Master Mendelian Disorders & Molecular Basis)
- *Mutations, Mendelian Disorders, Molecular Diagnosis, Chromosomal Disorders, Complex Multigenic Disorders* (Genetic Disorders Pathology Crash Course: Exam Revision Notes)
Study material on Complex Multigenic
- COMPLEX MULTIGENIC AND CYTOGENETIC DISORDERS - 50 MCQs
- Complex Multigenic and Cytogenetic Disorders MCQs
- Genetic Disorders MCQs Examination (Part 2)
Practice questions on Complex Multigenic
In complex multigenic disorders, what percentage of type 1 diabetes risk is contributed by a few HLA alleles?
- 25%
- 40%
- More than 50%
- 75%
- Usually mediated by non-specific mechanisms
Answer: C. Of the 20 to 30 genes implicated in type 1 diabetes, a few HLA alleles contribute more than 50% of the risk, demonstrating that different polymorphisms vary significantly in their contribution. ---
According to the common disease-common variant hypothesis, complex multigenic disorders occur when
- A single mutation has high penetrance
- Many polymorphisms with modest effects are co-inherited
- Environmental factors alone cause disease
- Chromosomal abnormalities are present
- Primarily an incidental laboratory finding
Answer: B. Complex multigenic disorders occur when many polymorphisms, each with a modest effect and low penetrance, are co-inherited according to this hypothesis. ---
Which statement regarding complex multigenic disorders is false?
- Environmental influences hardly modify their phenotypic expression
- Caused by interactions between variant genes and environment
- Occur when many polymorphisms are co-inherited
- Some polymorphisms are shared across diseases, others disease-specific
- Normal phenotypic traits are governed by multigenic inheritance too
Answer: A. Gene-environment interaction is a defining hallmark of multigenic disease — environment strongly modifies expression. ---
Which best describes complex multigenic disorders?
- Caused by single gene mutations only
- Caused by interactions between gene variants and environmental factors
- Always follow Mendelian inheritance
- Never show familial clustering
- disorders are caused by interactions between variant forms of genes and environmental factors.
Answer: E. Complex multigenic (or multifactorial/polygenic) disorders are caused by interactions between variant forms of genes and environmental factors. ---
Assigning a disease to complex multigenic inheritance depends first on
- Molecular testing
- Familial clustering and exclusion of mendelian/chromosomal transmission
- Environmental factors only
- Age of onset
- Reduced by routine feedback control
Answer: B. Attribution to complex multigenic inheritance depends first on familial clustering and the exclusion of mendelian and chromosomal modes of transmission. ---
In complex multigenic disorders, what percentage of type 1 diabetes risk is contributed by a few HLA alleles?
- 25%
- 40%
- More than 50%
- 75%
Answer: C. ** Of the 20 to 30 genes implicated in type 1 diabetes, a few HLA alleles contribute more than 50% of the risk. ---