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MCB1 Block 4 > Nonsense-Mediated RNA Decay > Flashcards

Nonsense-Mediated RNA Decay Flashcards

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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
Different enhancers can direct expression of the same gene in different _____
tissues
26
What is lobar holoprosencephaly
only a part of the brain doesn't develop into two hemispheres normally
27
where isi the mutation in lobar holoposencephaly
point mutation in enhancer activating SHH expression in specific part of brain during development
28
What is SBE
SHH brain enhancer
29
What is ZRS
limb specfific enhancer in LMBR1 described previously
30
Enhancer mutations far upstream of SHH result in what
polydactyl not holoprosencephaly
31
Where is mutation in Campomelic Dysplasia
Sox9 (or in 2 enhancers)
32
skeletal abnormalities, undereveloped shoulders, 11 instead of 12 ribs, is what disease
campomelic dysplaia
33
Where is Sox9 gene?
Acts downstream of SRY gene (SRY is in charge of making males males)
34
46 XY who have campomelic dysplasia have what else happen
ambiguous female genitalia
35
in lactose intolerance what is not expressed
lactase
36
what disease has inability to metabolize lactose
lactose intolerance
37
how much of the world is affected by lactose intolerance and why
75% - it is wild type, the normal mammalian phenotype
38
what does lactose need to be turned into to have body process
galactose & glucose
39
in regards to lactase what is the mutant phenotype
lactase peristence
40
what does LP stand for
lactae persistence
41
In people of european descent what is the most common mutation that leads to lactase persistence?
C to T substitution that leads to increased expression and maintains intestinal expression of lactase
42
In non-caucasians, where are mutation for lactase persistence?
in different place than for those of european descent
43
If it's gain of function what is MOI
AD
44
For every deletion syndrome there is what
corresponding duplication syndrome
45
what is the clinical presentation of deletion vs duplication syndrome
some overlap in clinical phenotype (esp mental retardation and behavioral problems) will usually see opposite phenotypes
46
About 1/2 of our genes are expressed where
brain
47
What is a chromosomal mutation
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
What does WBS stand for
Williams-beuren syndrome
49
Growth abnormalities, very happy, cardiac problems, mentally challenged, is what disease
WBS
50
Where is chromosomal deletion that causes WBS
7q11.23
51
What is one of the important deleted genes in WBS?
Elastin (ELN)
52
What does ELN stand for
Elastin
53
In WBS the abnormal pairing results in what
deletion & duplication products
54
In chromosomal diseases for every deletion there should be corresponding
duplication
55
b/w deletion and duplication which has more severe phenotype
deletions
56
Autosomal monosomy is always
lethal
57
Is autosomal trisomy alwyas lethal
no
58
What is the duplication counterpart to Williams syndrome
WBSCR duplication syndrome
59
what does WBSCR stand for?
William syndrome critical region
60
What disease is all neuropathies and has locus heterogenity
charcot-marie tooth disease
61
what is CMT1A a family of
charcot-marie-tooth disease
62
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 ```
CMT1A
63
What does HNPP stand for
Hereditary Neuropathy with Liability to Pressure Palsies (HNPP)
64
Both HNPP and CMT1A map to what chromosome
17p11.2
65
What gene is affected in HNPP & CMT1A?
PMP22
66
What is PMP22 function?
major transmembrane protein in myelin
67
What causes CMT1A and HNPP?
misalignment and recombination b/w flanking repeats
68
If PMP22 has gain of function what disease
CMT1A
69
If PMP22 ha loss of function what disease
HNPP
70
If there are null mutations in PMP22 what disease
HNPP
71
Missense mutations in PMP22 are what severity vs. CMT1A?
more severe
72
Missense mutations in PMP22 are what severity vs. CMT1A?
more severe
73
``` 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? ```
``` Short philtrum Thin lips Larger teeth Arched palate Narrow forehead Normal periorbital area Severe expressive language delay Relative strength in spatial skills ```
74
what is gene conversion
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
What is the result of gene conversion?
it depends on the mismatch repair
76
What does CAH stand for
congenital adrenal hyperplasia
77
What gene is involved in CAH
CYP21A2 (21 hydroxylase)
78
What is CAH?
a group of diseases resulting from deficiencies of enzymes involve din glucocorticoid or mineralcorticoid or sex steroid production
79
female pseudohermaphroditism | male hypospadias is what disease?
CAH
80
what is hermaphroditism
sex reversal
81
what is pseudohermaphroditism
if you are 46 XX you will have external male genitalia but internal female genitalia
82
what is male hypospadias
urethra is under the penis
83
In disorders of steroid metabolism what is decreased
aldosterone & cortisol
84
in disorders of steroid metabolism what is increased
androgens
85
What is the most common type of CAH
21 hydroxylase deficiency
86
excessive adrenal androgen biosynthesis decreased aldosterone and coritosl salt wasting, hypoglycemia, impaired glucose regulation is what disease
21-Hydroxylase deficiency
87
Which is the milder form of 21 hydorxylase deficiency?
non-classic form

MCB1 Block 4 (17 decks)

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