Complex/Non-Mendelian Inheritance Flashcards
List five examples of non-Mendelian inheritance
Linked inheritance Intermediate phenotype Incomplete penetrance Genomic imprinting Extranuclear inheritance Anticipation
What is penetrance?
the frequency with which a trait is manifested by individuals carrying the gene
What is incomplete penetrance?
gene is not phenotypically expressed in all members of a population that have the gene
What are two examples of penetrance mechanisms?
Genetic modifiers (e.g. polymorphisms)
Environmental factors
What is genomic imprinting?
the inheritance of one working copy of a gene, either from the maternal or paternal sides
the other, non-functional gene, is ‘silent’ (turned off)
From which parent are mitochondria inherited?
the mother (none from father as sperm degenerate after fertilisation)
Why do mitochondria have an increased mutation level?
- no DNA repair system
- no protective protein e.g. histones
- damaged by oxygen free radicals
What is homoplasmy?
all mitochondrial DNA is the same (no disease)
What is heteroplasmy?
more than one type of mitochondrial DNA is present (increased amount of diseases caused)
Give an example of a condition caused by triplet repeat expansion
Huntington’s disease (repetition of CAG triplet)
What is triplet repeat expansion?
repetition of a particular sequence of three nucleotides in the genetic code of an individual which can give rise to disease
number if repeats in the code can increase through the generations
What is UPD?
Uniparental disomy
where a whole chromosome pair comes from only one parent
Give two examples of conditions caused by UPD
Angleman Syndrome (maternal UPD of chromosome 15)
Prader-Willi Syndrome (paternal UPD of chromosome 15)
What are the clinical features of Prader-Willi Syndrome?
- hypotonia (decreased muscle tone)
- short
- obese
What are the clinical features of Angleman Syndrome?
- epileptic
- mental retardation
- awkward gait
