single gene disorders Flashcards
(30 cards)
what do autosomal dominant disorders imply about the wild-type gene?
the wt is recessive
how are autosomal dominant disorders acquired?
inherited or random mutation
how are autosomal dominant genes passed down?
- through mendelian laws of inheritance
- seen in every generation
name an example of an ADD
huntington’s disease
what is the genetic basis for HD?
- more than 36 polyglutamine (CAG) repeats
- DNA polymerase skips over these regions
define genetic anticipation
CAG repeats increase per generation, so the onset of HD is earlier in progeny
what is the effect of polyQ in cells?
- misfolded proteins form protein aggregates
- forms inclusion bodies in neurons which impairs axonal transport
- causes mitochondrial dysfunction
what do autosomal recessive disorders imply about the wild-type gene?
the wt is dominant
how are ARD passed down per generation?
via mendelian inheritance laws
name an example of an ARD
cystic fibrosis
name the mutated protein in cystic fibrosis
CFTR
what is the role of CFTR?
- a transmembrane protein that allows the influx of Cl- ions
- this keeps the mucous on the airways surface layer thin and runny
what percentage of CF sufferers have the delta-F508 mutation?
70%
define private mutations in CF
additional mutations other than delta-F508
are CF suffer homozygous or heterozygous for the disease?
can be either - CF sufferers can inherit the same or different mutations of the disease
name the 6 mutation types
- no protein
- less protein
- no function
- less function
- no traffic
- unstable
are x-linked disorders usually dominant or recessive?
usually recessive
how do sons inherit x-linked disorders?
from their mothers; they have a 50% chance of inheriting the disease
how do daughters inherit x-linked disorders?
- both parents must have the mutation
if a mother has an x-linked disorder, what is the chance that she will pass the gene onto her daughter?
50%
can fathers pass x-linked disorders to their children?
they can only pass the gene over to their daughters
sons only inherit the y-chromosome from their fathers
what proportion of the population have cystic fibrosis?
ans: 2..
1 in 2 000
what proportion of the population are carriers for the CFTR mutation?
ans: 2..
1/22
name an example of an x-linked disease
duchenne’s muscular dystrophy
