albinism an angelman quiz Flashcards
(67 cards)
Angelman syndrome defined by
mental impairment, excessively happy demeanor, jerky movements, sleep disturbance
what jerky movements in angelman are common
hand flapping
how many ppl are affected by angelman
1 in 20,000 live births
does Angelman SYndrome present the same phenotype in its patients
yes
the multiple mechanisms for angelman phenotype
imprinting and deletion
imprinting errors
uniparental disomy
genetic imprinting
when one copy of a gene is “turned off” after it is inherited
genetic imprinting is usually caused by
methylation
methylation
additon of methyl group -CH3 o a gene
the methyl group in genetic imprinting does what
blocks transcription from happening> DNA never becomes RNA>never makes protein
(imprinting) for many genes, either the mother’s chromosome or the father’s chromosome is
systematically silenced
what is a gene always silenced in sperm, not in eggs
UBE3A
where is UBE3A located on
on the 15th chromosome
UBE3A codes for
protein E6-AP
E6-AP is involved in what
the ubiquitination process
what is ubiquitination process
cell’s way of targeting and destroying certain proteins
since the father’s copy of UBE3A is always silenced,
the mother’s copy becomes extremely important
in about 75% of cases of Angelman
a chromosomal deletion mutation leads to the complete deletion of this gene in the egg
if there is a deletion of UBE3A in the egg
since the father’s copy is silenced the baby will have no functioning copies of E6-AP
UBE3A gene is located very close to
P gene (causes type 2 albinism)
since UBE3A is so close to P gene
chromosomal deletion mutation will affect both genes» albinism more common in people with Angeman
what percentage of Angelman is an imprinting error
20%
what is the imprinting error that causes Angelman
the mother’s copy of the gene is methylated w/ the fathers
result of imprinting error
both copies are off, phenotypes look the same as if mom’s gene is missing
rare cases of Angelman syndrome
cause by uniparental disomy
