Genetic basis of complex inheritance Flashcards
What rule does Mendelian inheritance follow
Law of dominance
The Law of Segregation
The Law of Independent Assortment.
An intermediate phenotype is a result of
Non mendelian inheritance
What are the factors contracting to non mendelian inheritance
Incomplete penetrance
Genomic printing from parental genes
mitochondria mutations
anticipation
Define penetrance
the frequency with which a trait is manifested by individuals carrying the gene
What is an example of a disease thats shows 100% penetrance
cystic fibrosis
CFTR mutation
What two factors contribute to the severity of a mutational human disease
Genetic modifiers
Environmental Factors
Define Genomic imprinting
only certain genes are expressed from parents e.g. if the allele inherited from the father is switched of silenced only the allele from the mother is therefore expressed
Define Bi-allelic
Both parental genes are expressed
What is uniparental disomy
Inheritance of chromosomal pair from one of the parental
What is a genetic modifier
Genes that have small quantitative effects on the level of expression of another gene.
What are Epigenetic modifications
Parental changes in gene function that cannot be explained by changes in DNA sequences
what do imprinted genes have a higher risk of
genetic disease
How can Imprinting errors occur
Deletion
Uniparental disomy
What are the three pathways that can cause Uniparental disomy
Trisomy/monsomy rescue
mitotic error
What are examples of uniparental disomy disorders
Gynogenic (2 maternal= ovarian teratoma)
Androgenic (2 parental = Hydatidiform mole, womb mass)
What are examples of imprinting disorders within chromosomal region 15q11-13
Angelman syndrome - paternal
Prader willi syndrome - maternal
Why is the mitochondria a mutational hotspot
lack of efficient DNA repair system
Lack of protective proteins
damage by free radicals
What is homoplasmy and heteroplasmy
no mutated mitochondria
mutated mitochondria
Where are mitochondrial diseases most likely to occur
tissue with high metabolic demand = myopathies
what are the examples of mitochondrial diseases
Diabetes mellitus and deafness (DAD)
Leber’s hereditary optic neuropathy (LHON) -loss of central vision
Leigh’s syndrome - neurological disorder
What is anticipation
Disease presents at earlier age become more apparent with each generation and can increase severity in succeeding generations.
Example of anticipation triplet repeat expansion
Huntington’s disease
Myotonic dystrophy
Fragile X syndrome
what happens in triple repeat diseases
Mutated triplet ions located everywhere and during meiosis, unstable repeats can undergo triplet expansion therefore the germ cells produce greater number of repeats than are found in the somatic tissues
