Phenotypic variability Flashcards
How do gene/environmental interactions contribute towards phenotypic variance?
Contribute to the progression and outcome of the disease for each patient.
Affects prognosis
Which genes are mutated within MEN1?
Mutation within tumor suppressor gene (synthesizes menin).
Which protein is mutated within hereditary hemochromatosis?
HFE
Which hormone regulates iron release within enterocytes?
Hepcidin
What is the pathophysiology of hereditary hemochromatosis?
HFE protein regulates iron levels within hepatocytes by preventing transferrin from binding to transferrin receptor I. HFE mutation reduces iron transportation into the liver, therefore hepcidin synthesis is reduced. This causes increase ferroportin release of iron from enterocytes, resulting in iron overload.
Why are women more likely to be protected from hereditary hemochromatosis?
Menstrual bleeding
What are genetic modifiers?
Life-course of disease and symptoms present are modified by presence of other genes. These gens can either improve or worsen the condition.
Which protein is involved in muscular dystrophy?
Dystrophin
Which are the two main muscular dystrophy conditions?
Becker muscular dystrophy
Duchenne muscular dystrophy
When is the age of onset of Becker muscular dystrophy?
12 years old, loss of ambulation varies from adolescence onwards
When does death usually occur with patients expressing BMD?
Death in the fourth/fifth decade
Which type of gene mutation is associated with muscular dystrophy disorders?
Deletions
How does a gene mutation cause DMD?
A deletion within the dystrophin gene causes a frameshift deletion, thus this means no active dystrophin is produced (triplet of a sequence of bases altered, altering codon sequence)
Presence of premature stop codon
How does BMD mutation occur?
Deletion causes stop codon, therefore a truncated functional dystrophin protein is produced
What are unstable gene mutations?
Diseases termed trinucleotide repeat disorders, the underlying cause of the disease is trinucleotide repeat expansion. Mutation whereby a region of three repeated nucleotides within the genome increases in frequency during DNA replication.
