Gnetic basis of complex inheritance Flashcards
(20 cards)
Mendelian Inheritance (3)
Law of dominance
Law of segregation
Law of independent assortment
Non- mendelian inheritance
Does not fit in with Mendelian inheritance due to gene conversion and the ability of an intermediate phenotype
Anticipation
Eg triple repeat expansion
Extracellular inheritance
Eg mitochondrial DNA
Genomic printing
Variants from parents
Incomplete penetrance
Environmental factor
Genetic modifiers
Penetrance
Frequency with which trait is manifested by individuals carrying the gene
% with trait (mutant)/% with trait (wild) = RISK
Genetic modifiers
Genes that have small quantitative effects on level of expression of another gene - many involve polymorphism
Genomic imprinting
Genes expressed from only 1 chromosome so is parent of origin dependent and there is a higher risk of causing genetic disease
Epigenetic modifications
Heritable changes in gene function not explained by changes in DNA
Cytosine ( mC)
Induces structural adaption of chromosomal region so as to continue altered activity states
Anticipation - triple repeat
Disease presents at earlier age and/or increasing severity with age eg Huntingtons and myotonic dystrophy
Genetic mechanisms
Deletion, point mutation, imprinting error and uniparental disomy
Imprinting error (P)
Loss of maternal expression causing Angleman syndrome - epilepsy, awkward gait and retardation
Imprinting error (M)
Prader -wili syndrome - hypotonia short and obese
Uniparental disomy
Inheritance of a chromosome pair from one parental origin
Gyogenic
2 Maternal
Mass of embryo and ovarian teratoma
Androgenic
2 Paternal
Mass of placenta and Hydatidiform male
What does mitochondrial inheritance effect?
Tissue with high metabolic demand
Does mitochondrial DNA have a higher or lower mutation rate than nuclear DNA?
Higher - 100 fold more
Lack of DNA repair system and protective histones
Oxygen release radicals that attack DNA (mtDNA)
