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pathophysiology > albinism an angelman quiz > Flashcards

albinism an angelman quiz Flashcards

1
Q

Angelman syndrome defined by

A

mental impairment, excessively happy demeanor, jerky movements, sleep disturbance

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2
Q

what jerky movements in angelman are common

A

hand flapping

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3
Q

how many ppl are affected by angelman

A

1 in 20,000 live births

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4
Q

does Angelman SYndrome present the same phenotype in its patients

A

yes

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5
Q

the multiple mechanisms for angelman phenotype

A

imprinting and deletion
imprinting errors
uniparental disomy

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6
Q

genetic imprinting

A

when one copy of a gene is “turned off” after it is inherited

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7
Q

genetic imprinting is usually caused by

A

methylation

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8
Q

methylation

A

additon of methyl group -CH3 o a gene

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9
Q

the methyl group in genetic imprinting does what

A

blocks transcription from happening> DNA never becomes RNA>never makes protein

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10
Q

(imprinting) for many genes, either the mother’s chromosome or the father’s chromosome is

A

systematically silenced

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11
Q

what is a gene always silenced in sperm, not in eggs

A

UBE3A

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12
Q

where is UBE3A located on

A

on the 15th chromosome

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13
Q

UBE3A codes for

A

protein E6-AP

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14
Q

E6-AP is involved in what

A

the ubiquitination process

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15
Q

what is ubiquitination process

A

cell’s way of targeting and destroying certain proteins

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16
Q

since the father’s copy of UBE3A is always silenced,

A

the mother’s copy becomes extremely important

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17
Q

in about 75% of cases of Angelman

A

a chromosomal deletion mutation leads to the complete deletion of this gene in the egg

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18
Q

if there is a deletion of UBE3A in the egg

A

since the father’s copy is silenced the baby will have no functioning copies of E6-AP

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19
Q

UBE3A gene is located very close to

A

P gene (causes type 2 albinism)

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20
Q

since UBE3A is so close to P gene

A

chromosomal deletion mutation will affect both genes» albinism more common in people with Angeman

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21
Q

what percentage of Angelman is an imprinting error

A

20%

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22
Q

what is the imprinting error that causes Angelman

A

the mother’s copy of the gene is methylated w/ the fathers

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23
Q

result of imprinting error

A

both copies are off, phenotypes look the same as if mom’s gene is missing

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24
Q

rare cases of Angelman syndrome

A

cause by uniparental disomy

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25
Q

uniparental disomy is

A

rare condition where . zygote inherits two copies of a chromosome from one parent and no copies from another

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26
Q

two forms of uniparental disomy

A

uniparental isodisomy

uniparental heterodisomy

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27
Q

uniparental isodisomy

A

when a person inherits the SAME chromosome from a parent twice

28
Q

what cases would uniparental isodisomy happen

A

where a person would have a monosomy but undergoes a monosomy rescue

29
Q

what is a monosomy rescue

A

the single chromosome is duplicated

30
Q

a person who underwent a monosomy rescue will have

A

46 chromosomes, but 2 identical copies of the same one

31
Q

uniparental heterodisomy occurs when

A

there would be a trisomy but the zygote undergoes trisomy rescue

32
Q

trisomy rescue

A

one copy of the tripled chromosome discarded

33
Q

in how many cases of trisomy rescue will the embryo be normal

A

2/3

34
Q

in _____ cases of trisomy rescue___

A

1/3 cases, the embryo could inherit two copies of one parent’s chromosomes

35
Q

uniparental disomy can be the cause of AS when

A

-a person inherits 2 copies of father’s 15th chromosme, none from mom

36
Q

when 2 copies of father’s 15th chromosome inherited

A

both copies of father’s UBE3A gene silenced by methylation,&raquo_space;> AS phenotype

37
Q

AS rember

A

3 unique genotypes lead to same phenotype

38
Q

albinism

A

lack of pigment melanin

39
Q

two main types of albinism

A
  • oculocutaneous albinism

- ocular albinism

40
Q

oculocutaneous albinism

A

affects skin, hair , eyes

41
Q

ocular albinism

A

eyes only

42
Q

people w/ oculocutaneous albinism have ..

A

extremely fair skin, white-blonde hair, light blue eyes

43
Q

melanocytes do what

A

produce black pigment melanin that makes skin look dark

44
Q

melanocytes produce more melanin in response to

A

more sunlight exposure

45
Q

melanocytes package small amounts of melanin into

A

vessels called melanosomes

46
Q

melanosomes are passed on tp

A

superficial keratinocytes

47
Q

what does melanin do

A

absorbs UV rays from sun that can give u cancer

48
Q

skin color is determined by what

A

fatctor of number f melanosomes, how active melanocytes are

49
Q

what does NOT determine skin color

A

Aiyana

50
Q

A melanocyte generally ha

A

ling projections called dendrite that reach to more superficial layers

51
Q

dendrites of melancyte,…

A

passes melanosomes into outer cells

52
Q

albinism often causes

A

red eyes, ,

53
Q

albinism red eyes…

A

because w/ a total lack of pigment blood vessels in your can be seen, sensitive too sun

54
Q

what type of disorder is albinism

A

recessive

55
Q

most common mutation for oculocutaneous albinism comes in on

A

c

56
Q

TYR gene codes

A

enzyme tyrosinase

57
Q

two types type 1 of albinism

A

Type 1A: Amorphic mutation in TYR

Type 1B: Hypomorphic mutation in TYR

58
Q

types of type 1 of albinism look

A

same at birth, gradually type 1b is more dirty blonde``

59
Q

tyrosinase is

A

an enzyme that catalyzes an important step in the synthesis of melanin from tyrosine

60
Q

without tyrosinase

A

melanin’s precursor can’t be mDE, MELNIN CAN’T BE MADE EITHER

61
Q

melanin’s precursor

A

dopaquinone

62
Q

type 2 oculocutaneous albinism

A

comes from a deficiency in a transport protein found in the membrane of melanocytes

63
Q

the transport protein in the membrane of melanocytes

A

allows other proteins like tyrosinase to pass into the melanocyte from other cells, causing more melanin to be prduced inside

64
Q

gene for the transport protein in membrane of melanocyte

A

P gene, found on 15th chromosme

65
Q

the other types of albinism come from

A

mutations in other enzymes in the melanin synthesis pathway , not as common

66
Q

the other types of albinism can also come from

A

issues w transportation in melanocytes, storing melanin correctly etc

67
Q

ho many different genotypes of albinism have been seen

A

17+

pathophysiology (24 decks)

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