Genetics Flashcards
If sibling has disease, chance of another sibling being a carrier is 2/3 is only true for which mode of inheritance?
Autosomal recessive
In an autosomal dominant disease, what explains the disease frequency remaining the same?
Replaced by de novo mutations
If you don’t have a family history, what is the chance mom of an affected is a carrier in an X-linked disease?
2/3 chance mom is a carrier
If deletion is greater than 100 bp and known what test do you use to confirm diagnosis?
FISH
What test do you use for a series of known point mutations?
ASO
What test would you use for a CAG repeat expansion in SCA?
PCR and electrophoresis
What test would you use for a full mutation in fragile X?
Southern blot
What test would you perform if the gene location is know. But there is no time to identify mutation?
CA repeat, or RFLP/southern blot assuming information from linkage
Known mutation and les than 100 kb?
Southern blot
Severe hemophilia A is a result of?
Intrachromosomal rearrangement of F8 gene
What happens to restriction sites in rearrangements and what test would you use to identify it, as in severe hemophilia A?
Changes the length of DNA between restriction sites, use southern blot
Generally all mutations in same gene result in same phenotype describes what?
Haploinsufficiency
Different mutations in same gene may result in different phenotypes, as seen in FGFR
Gain of function
Different mutations in same gene yield a milder phenotype, as seen in collagens
Dominant-negative
Mutations that reduce or abolish function are known as?
Recessive disorders (autosomal or x-linked)
Premature termination codons do not result in what?
Truncated polypeptides
To observe GOF or Dom-neg effect, mutant proteinmp must be?
Synthesized
If you see same severity of phenotype from Missense and null mutations in the same gene then Missense mutation must result in?
Loss of function
PKU shows what type of heterogeneity?
Allelic
Most common CAH repeats are a result of what?
Recombination between misaligned 30kb repeats
When sequence of one gene is copied onto another we call that?
Gene conversion
X inactivation is?
Random
How can x-inactivation appear non-random?
As in girl with DMD, cells with mutation are unstable and die
Transcriptionally active chromatin is predominantly ____________ and has high levels of?
Unmethylated, acetylated histone tails
Prader-Willi syndrome is?
Paternal expression and maternal imprint of SNRPN region
Angelman syndrome is?
Maternal expression and paternal imprint in UBE3A region
Make carriers of fragile x premutation may develop?
Tremor/ataxia
Myotonic dystrophy is an example of?
Anticipation (with maternal expansion bias)
What are the polyglutamine diseases and what expansion is associated with them?
Huntington and SCA, exonic CAG expansion through paternal transmission
Alpha thalassemia is a result Of?
Deletion of alpha globin genes
Beta thalassemia results from?
Null mutation in beta globin
Sickle cell is a result of?
Missense mutation (A to T) in beta globin gene
For any gene expressed in multiple cell types, an enhancer mutation will only cause a phenotype in the cell type in which?
The enhancer was supposed to work
Multifactorial disorders are seen?
In small families, multiple disease genes/pt, low penetrance, unaffected individuals can also carry susceptible alleles
Poor metabolizers of codeine get?
No benefit from the drug
25-30% of prescription drugs are metabolized by?
Cytochrome P450s
FIRST screenings check for?
hCG, and PAP-A
Second trimester screening checks for?
AFP, hCG, UE3, inhibition A
What is the hardy Weinberg equation?
P^2 + 2pq + q^2 = 1
