Genetics Lecture 3 Flashcards
What is the defining symptom of alkaptonuria?
Urine turns black on exposure to air.
Is alkaptonuria genetic or acquired?
Is genetic.
What is the cause of albinism?
Inability to convert tyrosine to DOPA, a precursor to melanin.
What is the cause of phenylketonuria?
Inability to convert phenylalanine to tyrosine.
Define prototroph strain of neurospora.
Wild type neurospora able to grow on minimal media.
Define auxotroph strain of neurospora.
Mutant strain that cant live on minimal media.
How can the amino acid needed for auxotroph growth be isolated?
Grow on minimal media supplemented with one amino acid at a time.
Genetic diseases often involve disruption of a chain reaction. How can it be known which step of the reaction is affected?
Grow on minimal media supplemented sequentially with reaction substrates.
What is the incidence of phenylketonuria?
1/12,000
Mutation to what enzyme causes phenylketonuria?
Phenylalanine hydroxylase.
What happens to phenylalanine in the body of an individual with phenylketonuria?
Accumulates, and is converted to phenylpyruvic acid.
Define the pleiotropic effect using phenylketonuria as an example.
When a gene influences more than one seemingly unrelated phenotypic effects. phenylketonuric individuals will have no thyroxine, adrenaline, or melanin.
Can phenylketonuria be cured or managed?
No cure, perhaps in gene therapy.
Can be managed with diet restrictions.
Is lesh-nyham syndrome a dominant or recessive gene? Is it a fatal gene?
Is a fatal recessive gene.
What is the incidence of lesh-nyham syndrome?
1/10,000
Lesh-nyham syndrome is caused by a deficiency of which enzyme? What is a conseqeunce of this?
Phyoxanthine-guanine phosphoribosyl transferase.
Causes pruines to accumulate, and converted to uric acid.
What are the main symptoms of lesh-nyham syndrome?
Severe neurological symptoms, including paralysis.
What is the incidence and rarity of tay-sachs disease like in different populations?
Rare in the general population, but high in the Ashkenazi Jews, with an incidence of 1/3,600.
Tay-sachs disease is caused by a deficiency in that gene? What does it encode for? What does it do?
Defect in HexA coding for the lysozomal enzyme N-acetylhexosaminidase A.
Cleaves group from brain ganglioside Gm2, which accumulates in tay-sachs disease individual.
What are the symptoms of tay-sachs disease? What is the prognosis at birth?
Reaction to sharp sounds, and a cherry-coloured spot on their retina.
Prognosis is 1 year afterbirth.
Is sickle-cell disease dominant or recessive? Is it lethal?
Recessive, and non-lethal.
What is sickle-cell disease a mutation to?
Haemoglobin, B subunit.
What haemoglobin composition do heterozygous individuals of sickle-cell disease have?
Half normal, half sickle celeld.
What amino acid change is sickle-cell disease caused by, and how does this change induce the disease?
Point mutation changing Glu to Val, which is hydrophobic. This creates a hydrophobic patch on the complete haemoglobin, causing them to clump together and precipitate, warping the cell, and causing loss of oxygen capacity.
What is the most common lethal disease amongst Caucasians?
Cystic fibrosis.
What is the incidence of cystic fibrosis in newborns, and carriers?
1/2,000 newborns
1/23 are carriers.
What are 5 symptoms of cystic fibrosis?
Pulmonary, pancreatic, and digestive dysfunction.
High viscosity mucus accumulates in the lung, leading to secondary infection.
Dysfunction of what protein causes cystic fibrosis? What is it normally?
The cystic fibrosis transmembrane conductance receptor - CFTR, a chlorine channel.
What kind of mutation causes cystic fibrosis?
Deletion of 3 base pairs - one missing amino acid.
