Section IIB Flashcards
(23 cards)
What are the three kind of base substitutions and what are their consequences?
- Silent substitutions: no consequence
- Missense mutations: change in **amino acid **
- nonsense mutations: Stop codon
What are the donor and acceptor sequences in splice sites? How can a mutation here cause an issue?
- GT…AG rule
- A mutation in the exon can move the splice site to within the intron or to take out part of the exon.
- sometimes a second GT donor site is created withen the exon resuling in abnormally and normally spliced mRNA products.
- Can activate cryptic sites
What is the major consequence of a 3bp insertion or deletion mutation?
-Adds or deletes one amino acid but does nt affect the reading frame
What is the major consequence of an inserition or deletion that is not a multiple of 3?
-it causes a frameshift that changes all downstream amino acids and will generally terminate the polypeptide early.
What are the properties of a gain-of-function muataion?
- typically domnant disorders
- result in overexpression of the product
Are loss-of-function mutations more often recessive or dominant?
- recessive unless 50% of protein product is not enough to maintain normal function, then it is dominant
- termed hypoinsufficiency
How many alpha and beta chains of Hb gene does a normal human have?
two beta
four alpha
which chain is defficient in alpha-thalassemia? what happens to the chain that is in excess?
- alpha chain is defficient, so the beta chain is in excess
- the Beta chains form homotetramers which have reduced O2 capacity leading to hypoxia
What happens to the excess alpha chains in Beta-thalassemia?
-alpha-chains form homotetramers that precipitate and damage the erythrocyte and lead to premature RBC destrction and anemia
What tyoe of mutation is induced by UV light?
base pair substitution
-pyrimidine dimers
What is the best known mutation hot spot?
- dinucleotide GC regions which are mostly 5-mythylcytosine
- cytosine is easily demethylated to thymine and a mutation occurs.
What DNA repair mechanism is responsible for repairing pyrimidine dimers?
-Nucleotide excision repair system
What does a defect in NER lead to?
Xeroderma pigmntosum
What is the cause of Cockayne Syndrome?
-defeective repair of UV-induced damage in transcriptionally acitve DNA
–very similar to XP
What is the cause and symptoms of Fanconi anemia?
-Cause unknown
–Anemia, leukemia susceptibility
What is the cause and symptoms of bloom syndrome?
-muatations in the reqQ helicase family
–growth deficiency, immunodeficiency, chromosome instability
What are the causes and symptoms of Werner syndrome?
-mutation in the reqQ helicase family
–Premature aging (cataracts, osteoporosis, etc.)
What are the causes and symptoms of ataxia-telangiectasia?
-defects in halting the cell cycle after DNA damage.
–cerebellar ataxia, telangiectases
What are the causes and symptoms of HNPCC (hereditart non-polyposis colorectal cancer)?
-mutations in any 6 DNA mismatch-repair genes
What antibodies and antigens are present in the following cases:
- A+
- A-
- AB+
- AB-
- O+
- O-
- Type A, B and Rh antgen
- Type A, B antibody
- Type AB, neither A nor B but +Rh antigen
- same, no Rh antibody
- type O, Both A, B and Rh antigen
- Same as above, no Rh antigen
What is the multiplication rule?
-What is the probability that a couple with have all four boys?
- if trials are independant, the probability of obtaining a given outcome in both trials is the product of the individual probabilities.
- (1/2)(1/2)(1/2)(1/2)= (1/16)
What is the addition rule?
-what is the probability that a couple with 4 children will have either all boys or all girls?
- states that the probability of one outcome or another is simply the added probabilities.
- (1/16)+(1/16)= (1/8)
