The Genetic Basis of Complex Inheritance Flashcards
Mendelian Inheritance
The Law of Dominance
The Law of Segregation
The Law of Independent Assortment
Non-Mendelian Inheritance
Does not fit in with Mendelian’s Law
Several variants in several genes acting together
Pattern of Non-Mendelian Inheritance
Incomplete Penetrance Genomic imprinting Extranuclear Inheritance Anticipation Complex
Incomplete Penetrance
Environmental factor
Genetic Modifiers
Genomic Imprinting
Variants from parents
Genes from only one chromosome is expressed
Dominance is meaningless
Extranuclear Inheritance
Mitochondrial mutations
Anticipation
Triplet repeat expansion
Complex
Multi-genic risk
Penetrance
the frequency with which a trait is manifested by individuals carrying the gene
100% Penetrance
Cystic Fibrosis
50% Penetrance
Ovarian Cancer
Genetic Modifiers
Genes that have small quantitative effects on the level of expression of another gene
Environmental Factors
Lifestyle, Diet, Smoke, Alcohol, Drugs, Stress, Air Pollution, Chemicals, Infection
Epigenetic Modifications
Heritable changes in gene function that cannot be explained by changes in DNA sequence
Methylation
Addition of a methyl group to DNA. Can change the activity of the DNA without changing the structure
Uniparental Disomy
Inheritance of a chromosome pair from one parental origin and no copy from the other parent
Gynogenic
2 maternal genomes
Mass of embryo
Ovarian teratoma
Androgenic
2 Paternal genomes
Mass of placenta
Hydatidiform
Human models of imprinting disorders
Angelman Syndrome
Prader-Willi Syndrome
Angelman Syndrome (4)
Epilepsy
Mental retardation
Awkward Gait
Inappropriate laughter
Prader-Willi Syndrome (4)
Hypotonia
Mental retardation
Short stature
Marked obesity
Chromosomal region for AS and PWS
15q11-13
Mitochondrial Inheritance
Maternal
Paternal is destroyed during fertilisation
Heteroplasmy
Mitochondira that have a mutation in the mtDNA and some that do not
Homoplasmy
Cell that has a uniform collection of mtDNA (either all normal mtDNA or completely mutant mtDNA)
Mitochondrial Disease affects____
Tissues with high metabolic demand
Mitochondrial Myopathies
MERRF, MELAS, CPEO, LHON, Leigh’s Syndrome, DAD
Three parent baby
Healthy nuclear DnA removed from mother
Transported into donor egg with healthy mitochondrial DNA
Reconstructed egg fertilised with sperm and implanted
Anticipation- Triplet Repeat Expansion
Disease presents at earlier age and/or increasing severity in succeeding generations
Examples of triple repeat disease
Huntington’s disease
Myotonic dystrophy
Fragile X syndrome
Multigenic/Complex Inheritance is often seen in
heart disease, breast cancer, autism
Multigenic/Complex Inheritance consist of
Multiple low penetrance variants
