L21: Autosomal dominant disorders Flashcards
What are the main classes of genetic disorder
- single gene/ Mendelian conditions
- chromosomal
- mitochondrial
- Multifactorial
Is autosomal dominant heterozygote or homozygous
Heterozygote as you only need one dominant copy of the altered gene to get the condition
What are common autosomal dominant conditions
- dominant otosclerosis
- familial hypercholesterolaemia
- neurofibromatosis
- myotonic dystrophy
What are the chances of an affect parent with a normal parent to have an affected child
50 percent
In an autosomal dominant condition is there half the concentration of structural protein and receptors or enzymes
Structural proteins and enzymes which give the clinical effect
In an autosomal recessive condition is there half the concentration of structural proteins and receptors or enzymes
Enzymes which show no clinical effect
How do you diagnose an autosomal dominant condition
Sequencing DNA
- show that a mutation alters they function and structure of a protein
- compare the mutation to affected individuals in the family
- compare with non affected individuals in the family
What are the 5 exceptions to autosomal dominant recessive inheritance
- variation in expression
- incomplete penetrance
- new mutation
- anticipation
- gonadal mosaicism
What is variation in expression
When there a different signs of the same disease so some people are not aware of the disease
What is incomplete penetrance
The person develops the signs later on in life- age related penetrance
What is new mutation
Two non affected parents can get a child with an autosomal dominant condition due to a new mutation occurring in sperms
Why does new mutation chances increase with paternal age
As the spermatogonium undergoes cell division the likelihood of creating a new mutation increases
What is anticipation
In increasing generations the age onset is reduced and severity of the phenotype increases
Why does anticipation develop with generations
The number of triple repeats above the normal limit is inherited
What is mosaicism
Gonadal mosaicism can cause it to pass on.
