SIngle Gene disorders Flashcards
2 autosomal Dominant types?
Loss of function- defects in structural proteins
Gain of function- normal proteins with toxic properties. (gain of function bad e.g. huntington disease)
What is a disease that is autosomal dominant and has spots on the eye?
Neurofibromatosis Type 1
This is a diagnostic tool in the clinical setting for Neurofibromatosis type 1. (know it)
Lisch Nodules
Important genetic concept that is epitomized by Neurofibromatosis Type 1.
variable expression- even within the same family
What is a disease that is autosomal dominant that involves pleiotropy?
Marfan syndrome
When a single mutation affects multiple organ systems a common feature of many genetic diseases.
Pleiotropy
What are some disorders involved with marfan syndrome?
Hypermobile joints Cardiovascular disease Skeletal abnormalities (thin long limbs and fingers)
What is the most common single gene disorder in the world and is autosomal recessive?
Thalassemia (‘thalassa’ means sea)
Thalassemia causes premature death of cells destined to become red blood cells- results in ______________.
Hemolytic anemia
What disease makes you resistant to malaria?
Thalassemias
Males need only one copy of a defective ________ gene whereas females would need 2 copies of a defective __________ gene to show symptoms.
X-linked gene
Therefore phenotype issues are much more common in males.
Bleeding into the joints, causes swelling and loss of joint mobility
Hemarthosis
Most frequent cause of death with someone that has hemophilia A and B is what?
AIDS
Why is AIDS the most common cause of death with Hemophilia? (IMPORTANT)
The way we treat hemophilia is blood transfusion, in order to maintain blood clotting factor, you can’t treat the blood, so it may still contain diseases like AIDS.
Females have 2 copies of x chromosome, if no transcription control mechanism there would be a 2 fold excess of genes. What is the control mechanism?
X inactivation also called LYONIZATION (important)
What can explain why some female heterozygotes with one mutant X chromosome can show symptoms of an X-linked recessive disease.
X inactivation
What are some diseases that are rare cases of gene disorders that do not manifest until later in life?
Huntington disease (onset age 30 or 40s in first symptomatic generation) Myotonic Dystrophy- same as above
When the same disease phenotype can be caused by mutations in different loci (i.e. in different genes)
Locus Heterogeneity
All genetic disease begins with a __________.
New mutation
True/False: In cases with high mortality or low fertility it is often due to a new mutation. The disease will spread easily within the population.
False! people dying= hard to keep the mutation alive
new mutation typically get weeded out
This refers to diseases where the most recent generations of affected individuals have an earlier onset and more severe symptoms than previous generations.
Anticipation
Anticipation is most often associated with diseases caused by ___________________. (i.e. fragile X syndrome, myotonic dystrophy, Huntington disease)
Trinucleotide repeat expnsions
With anticipation, eventually (even though considered an adult disease) later generations symptoms may first appear in childhood, due to what?
Expansion of the trinucleotide repeat
What are the assumptions of HWE?
Large Population
Random Mating
Constant and predictable relationship between genotype frequencies and gene frequencies.
