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MCB1 Block 4 > Nonsense-Mediated RNA Decay > Flashcards

Nonsense-Mediated RNA Decay Flashcards

1
Q

Premature termination codons result in what regarding RNA

A

RNA degradation

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2
Q

premature stop codon results in what

A

null mutation - no protein

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3
Q

Evolutionarily, why might premature stop codons result in null mutation

A

to protect against dominant negative effects of truncated proteins

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4
Q

What does EJC stand for

A

exon junction complex

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5
Q

What do EJCs do

A

persis on mRNA after splicing and cytoplasmic transport

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6
Q

what displaces EJCs

A

ribosomes

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7
Q

What is nonsense mediated decay mechanism

A

it scans the 3’ stalled ribosomes for EJCs

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8
Q

every gene has what regulatory sequence upstream of it

A

promoter region

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9
Q

what is function of promoter

A

transcriptional initiation

level of expression

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10
Q

Explain EJCs

A

pg 135 ppt 2

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11
Q

Where are enhances and silencers located

A

a distance from gene, can be quite far away

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12
Q

enhancers do what to gene

A

activate

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13
Q

silencers do what to gene

A

inhibit gene

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14
Q

silencers are important for level and _____ of expression

A

specificity

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15
Q

mutations in proximal promoter elemtns usually do what to transcription

A

prevent

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16
Q

what effect is usually the effect of a mutation in proximal promoter element

A

null mutation

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17
Q

what is a common birth defect associated with severl syndromes

A

polydactylyl

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18
Q

What does SHH stand for

A

sonic hedge hog

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19
Q

what is the function of sonic hedge hog

A

morphogen - they signal for limb patterning and brain development

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20
Q

mutations in sonic hedge hog cause what

A

holoprosencephaly

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21
Q

what is holoposencephaly

A

forebrain fails to develop into 2 hemispheres - usually prenatal lethal

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22
Q

AD polydactylyl had linkage to what

A

SHH

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23
Q

Where is mutation in AD polydactylyl?

A

no mutations in SHH gene, enhancer has mutation on intron of LMBR1 gene

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24
Q

In LMBR1 is an ____ for SHH that does what

A

enhancer that activates expression specifically in the distal limb

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25
Q

Different enhancers can direct expression of the same gene in different _____

A

tissues

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26
Q

What is lobar holoprosencephaly

A

only a part of the brain doesn’t develop into two hemispheres normally

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27
Q

where isi the mutation in lobar holoposencephaly

A

point mutation in enhancer activating SHH expression in specific part of brain during development

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28
Q

What is SBE

A

SHH brain enhancer

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29
Q

What is ZRS

A

limb specfific enhancer in LMBR1 described previously

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30
Q

Enhancer mutations far upstream of SHH result in what

A

polydactyl not holoprosencephaly

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31
Q

Where is mutation in Campomelic Dysplasia

A

Sox9 (or in 2 enhancers)

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32
Q

skeletal abnormalities, undereveloped shoulders, 11 instead of 12 ribs, is what disease

A

campomelic dysplaia

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33
Q

Where is Sox9 gene?

A

Acts downstream of SRY gene (SRY is in charge of making males males)

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34
Q

46 XY who have campomelic dysplasia have what else happen

A

ambiguous female genitalia

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35
Q

in lactose intolerance what is not expressed

A

lactase

36
Q

what disease has inability to metabolize lactose

A

lactose intolerance

37
Q

how much of the world is affected by lactose intolerance and why

A

75% - it is wild type, the normal mammalian phenotype

38
Q

what does lactose need to be turned into to have body process

A

galactose & glucose

39
Q

in regards to lactase what is the mutant phenotype

A

lactase peristence

40
Q

what does LP stand for

A

lactae persistence

41
Q

In people of european descent what is the most common mutation that leads to lactase persistence?

A

C to T substitution that leads to increased expression and maintains intestinal expression of lactase

42
Q

In non-caucasians, where are mutation for lactase persistence?

A

in different place than for those of european descent

43
Q

If it’s gain of function what is MOI

A

AD

44
Q

For every deletion syndrome there is what

A

corresponding duplication syndrome

45
Q

what is the clinical presentation of deletion vs duplication syndrome

A

some overlap in clinical phenotype
(esp mental retardation and behavioral problems)
will usually see opposite phenotypes

46
Q

About 1/2 of our genes are expressed where

A

brain

47
Q

What is a chromosomal mutation

A

Gross changes to DNA within chromosomes, multiple genes involved
Eg. Duplications, deletions
Usually due to unequal crossing over during homologous recombination between repeat sequences

48
Q

What does WBS stand for

A

Williams-beuren syndrome

49
Q

Growth abnormalities, very happy, cardiac problems, mentally challenged, is what disease

A

WBS

50
Q

Where is chromosomal deletion that causes WBS

A

7q11.23

51
Q

What is one of the important deleted genes in WBS?

A

Elastin (ELN)

52
Q

What does ELN stand for

A

Elastin

53
Q

In WBS the abnormal pairing results in what

A

deletion & duplication products

54
Q

In chromosomal diseases for every deletion there should be corresponding

A

duplication

55
Q

b/w deletion and duplication which has more severe phenotype

A

deletions

56
Q

Autosomal monosomy is always

A

lethal

57
Q

Is autosomal trisomy alwyas lethal

A

no

58
Q

What is the duplication counterpart to Williams syndrome

A

WBSCR duplication syndrome

59
Q

what does WBSCR stand for?

A

William syndrome critical region

60
Q

What disease is all neuropathies and has locus heterogenity

A

charcot-marie tooth disease

61
Q

what is CMT1A a family of

A

charcot-marie-tooth disease

62
Q

Gross changes to DNA within chromosomes, multiple genes involved
Eg. Duplications, deletions
Usually due to unequal crossing over during homologous recombination between repeat sequences

Contiguous Gene Deletion Syndromes
Examples:
22q11 Deletion Syndrome (DiGeorge)
-thalassemia
Williams syndrome
A

CMT1A

63
Q

What does HNPP stand for

A

Hereditary Neuropathy with Liability to Pressure Palsies (HNPP)

64
Q

Both HNPP and CMT1A map to what chromosome

A

17p11.2

65
Q

What gene is affected in HNPP & CMT1A?

A

PMP22

66
Q

What is PMP22 function?

A

major transmembrane protein in myelin

67
Q

What causes CMT1A and HNPP?

A

misalignment and recombination b/w flanking repeats

68
Q

If PMP22 has gain of function what disease

A

CMT1A

69
Q

If PMP22 ha loss of function what disease

A

HNPP

70
Q

If there are null mutations in PMP22 what disease

A

HNPP

71
Q

Missense mutations in PMP22 are what severity vs. CMT1A?

A

more severe

72
Q

Missense mutations in PMP22 are what severity vs. CMT1A?

A

more severe

73
Q 
If Williams syndrome has Long philtrum
Full lips
Small teeth
Normal palate
Broad forehead
Periorbital fullness
 and Relative strength in expressive language
and Very weak spatial skills
what does WBSCR have?
A 
Short philtrum
Thin lips
Larger teeth
Arched palate
Narrow forehead
Normal periorbital area
Severe expressive language delay
Relative strength in spatial skills
74
Q

what is gene conversion

A

sequence of one gene is replaced by sequence of a similar but not identical allele or gene
it’s similar to recombination but nonreciprocal

75
Q

What is the result of gene conversion?

A

it depends on the mismatch repair

76
Q

What does CAH stand for

A

congenital adrenal hyperplasia

77
Q

What gene is involved in CAH

A

CYP21A2 (21 hydroxylase)

78
Q

What is CAH?

A

a group of diseases resulting from deficiencies of enzymes involve din glucocorticoid or mineralcorticoid or sex steroid production

79
Q

female pseudohermaphroditism

male hypospadias is what disease?

A

CAH

80
Q

what is hermaphroditism

A

sex reversal

81
Q

what is pseudohermaphroditism

A

if you are 46 XX you will have external male genitalia but internal female genitalia

82
Q

what is male hypospadias

A

urethra is under the penis

83
Q

In disorders of steroid metabolism what is decreased

A

aldosterone & cortisol

84
Q

in disorders of steroid metabolism what is increased

A

androgens

85
Q

What is the most common type of CAH

A

21 hydroxylase deficiency

86
Q

excessive adrenal androgen biosynthesis
decreased aldosterone and coritosl
salt wasting, hypoglycemia, impaired glucose regulation is what disease

A

21-Hydroxylase deficiency

87
Q

Which is the milder form of 21 hydorxylase deficiency?

A

non-classic form

MCB1 Block 4 (17 decks)

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