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Introduction to Genetics and Clinical Genetics Flashcards

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1
Q

Summarize the process of translation with all important enzymes.

A

1) RNA Pol binds to DNA.
2) Pol melts duplex DNA near transcription start.
3) Pol catalyzes phosphodiester link on 2 initial nucleotides and then advances down template strand 3’ to 5’ while synthesizing RNA 5’ to 3’
4) At transcription stop site polymerase releases DNA and RNA.

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2
Q

TFIID

A

Binds TATA box. Forms Pre-initiation complex.

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3
Q

TBP

A

TATA binding protein. Portion of TFIID that actually binds the TATA Box

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4
Q

TFIIB

A

Binds to PIC complex after TFIID

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5
Q

Core Promoter recognition sites and proteins.

A

TBP= TATA
TAF1 & TAF2= Inr
TAF6 & TAF9= DPE

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6
Q

Regulatory Promoter Sites

A 
Regulatory= promoter
Sites= GC, CCAAT
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7
Q

How does the mediator complex play a role in activation and repression?

A 
Activation= Coactivators and UAS activate mediator which activates TFIID and CFD
Repression= repressors inactivate mediator, UAS and activators. Mediator then inactivates TFIID and TBP
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8
Q

CTD

A

Carboxy Terminal Domain of RNA Pol. Plays 2 roles. Phosphorylation allows binding of RNA Pol to Core Promoter. Phosphorylation also allows the 7-MeG cap to use as a dock before capping RNA

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9
Q

Polyadenylation

A

The process of adding a PolyA tail via Pol(A) polymerase

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10
Q

PABPN1

A

Coats PolyA Tail. Stops synthesis at A x 200-300. trinucleotide repeat on this gene= oculopharyngeal muscular distrophy

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11
Q

5’ splice site is

A

G-GU

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12
Q

3’ splice site is

A

AG-G

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13
Q

mRNA splicing mechanism

A

two nucleophilic substitution reactions. catalyzed by the spliceosome= 300 proteins and several snRNPs

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14
Q

Lupus

A

Autoimmune disease. inflammatory symptoms due to autoimmune activity against snRNPs

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15
Q

zip code binding protein

A

attaches mRNPs to mRNA and motor proteins to move RNA to different regions of the cell for synthesis

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16
Q

modified scanning hypothesis

A

40s attaches. scans down 5’ to 3’ looking for AUG in proper context. ACCAUGG. when found 60s is recruited and complex begins translation

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17
Q

PABPI

A

Protein on Poly A tail which Regulates translation on 5’ end

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18
Q

tRNA role in translation

A

stacking. aminoacyl joins peptidyl +AA is stacked then converted to peptidyl

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19
Q

How do many antibiotics work?

A

inhibiting translation

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20
Q

Nonsense Mediated Decay

A

activates in RNA with premature stop codons. UTF2 binds UTF3 to form functional EJC. Complex bridges to ribosome and activates decay

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21
Q

Nonstop Decay

A

detects mRNA with no stop codon. Ribosome stalls on PolyA tail. PABPC1 flies off. either ski7 + degrades from 5 end or decapped and degrades 3-5

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22
Q

No Go Decay

A

degrades mRNA with no start codon. Dom34-Hbs1 binds to stalled ribosome and activates endonucleolytic cleavage and decay.

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23
Q

OPMD

A

Dysphagia, Dysphonia, Facial weakness, proximal limb weakness, 100% penetrant, autosomal dominant, trinucleotide repeat

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24
Q

Chromosome disorders

A

abnormalities in number or structure of chromosomes. not very common

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25
single gene disorders
alterations in coding sequence produce effects on function of protein. Usually mendelian based
26
Mitochondrial disorders
separate genome. can be disrupted in the same way as nuclear DNA but only maternally inherited. passed in cytoplasm of ovum.
27
Multifactorial disorders
combination of genes + environment
28
Polygenic
many genes play a role
29
teratogenic
environment primarily
30
Mosaicism
more than one genotype
31
Imprinting
parent of origin different in expression
32
uniparental disomy
both chromosomes from 1 parent
33
unstable triplet repeats
develop by expansion of normally present trinucleoside repeats
34
Inheritance Patterns tools work for which kind of disorders
single gene disorders. | e.g. pedigrees ect,
35
karyotype
detects alterations in chromosome # and very large mutations
36
FISH
synthesized DNA is labelled and denatured then paired to control and patient chromosomes.
37
Comparitive Genomic Hybridization
patient DNA and control DNA dyed and put in wells. cannot detect small deletions or duplication
38
What do we use for small mutations?
sequencing. individual gene, exome, or whole genome.
39
What are replication errors and how do we fix them?
base mismatches and base insertion. we fix it with mismatch repair which repairs individual base pairs.
40
Explain damage from cell environment and how it is repaired.
acid and heat of metabolism. also O2 radicals. removes purines. Uses BER
41
How does UV light damage cells and how does the cell fix it?
sunlight= creates DNA base adducts (cyclobutane dimers, 6-4 photoproduct). Direct repair via photolyase. NER.
42
Explain Ionizing Radiation and how do we fix it
xrays= single/ double strand bond breaks. Double strand breaks are repaired through homologous repair and end rejoining
43
Chemical exposure how does it happen and how do we repair it.
smoking, fossil fuel, foods. They create polycyclic aromatic hydrocarbons (PAH). heterocyclic amines.
44
What is interstrand crosslink repair?
It is a mechanism for repairing damage to one DNA strand. In G1 this takes the form of unhooking, translesion synth and then NER. In S phase there is no need to unhook so it goes straight to NER or homology driven repair.
45
xeroderma pigmentosum
defect in NER. 1000x increased risk of skin cancer. mutation in one of 8 XP genes used in NER complex.
46
Ataxia telangiectasia
mutations in ATM gene which is required for homologous recombination. ataxia in infancy. telegiectasia in childhood. bulbar conjunctivae immunodeficiency. may progress to malignant
47
Werner syndrome
premature aging, mutation in WRN gene which unwinds DNA for HR and replication. They get old person diseases.
48
Bloom syndrome
mutation in BLM gene which codes for helicases like WRN. Also important in decatenation. Skin sensitivity, narrow face, short, immunodeficiency, retardation, cancer risk.
49
BRCA1/ BRCA2 dependent inherited breast cancer
involved in homologous recombination repair, also ovarian and fallopian tumors.
50
Dominant Disorders
Marfans, Achondroplasia, NF1
51
Recessive Disorders
CF, PKU, most inherited metabolic diseases
52
What are some confounders to identifying causes in genetic disorders.
expressivity consanguinity de novo mutations mosaicism
53
germline mosaicism
presence of more than one genetically distinct cell line
54
penetrance
% of people who carry a pathogenic variant who express the trait
55
Variable expressivity
traits vary between individuals who carry the gene mutation
56
Retinoblastoma mutation
Autosomal Dominant. 10% have no symptoms. retinal tumor. reduced penetrance. 2 hit hypothesis (Knudsens)
57
NF1
neurofibromatosis 1. cafe au lait macules. axillary/inguinal freckling. neurofibromas. lisch nodules (iris). bony lesions and tibial bowing. penetrance 100%, expressively variable, de novo in 50%
58
Marfans
Michael Phelps disease. FBN1 gene (fibrillin). Major criteria: dialated aortic root and ectopia lentis. Other: skeletal changes, dural ectasia. 25% de novo. some mosaicism.
59
Achondroplasia
most common form of short limbed dwarfism. complete penetrance. fibroblast growth factor receptor gene (negative regulator)= activation mutation= lower bone growth. fathers germline.
60
traits of autosomal recessive diseases
complete penetrance, heterozygous= 50% function, usually enough early onset of symptoms
61
Sickle cell
Point mutation on HbS. HbS heterozygosity does seem to protect against malaria
62
CF
most common AR in Caucasians. sweat chloride test. infants= meconium ileus infancy= fail 2 thrive, pneumonia adults= azospermia, bronchiectasis.
63
PKU
inability to to process PHE. microcephaly, severe MR, epilepsy, variable expressivity, can pass maternally through placenta.
64
topoisomerase
slides down DNA unwinding superhelical turns
65
irinotecan
topoisomerase inhibitors are used in cancer chemotherapy
66
Pol A/primase
initiates DNA replication
67
DNA Polymerase gamma/ episilon
elongation
68
How does DNA Pol stay on DNA
beta clamp. clamp= PCNA brace= RFC
69
How does P53 affect DNA Pol
P53 to P21 to PCNA inactivation. inactivates DNA Pol
70
What controls the start of DNA replication
Origin of Replication Complex (ORC) binds to MCM helicase. inactivation happens when ORC binds to Cdc6
71
telomerase
enzyme that has RNA component. fills in 3' overhangs on okazaki fragments. telomerase higher in dividing cells
72
How does DNA repair replication errors?
``` proofreading= 1/10^7 mismatch= 1/10^10 ```
73
Lynch Syndrome
Heriditary Non-polyposis Colon cancer. inherited mutations in mismathc repair. MSH2 or 6. May be found by examining microsatellite instability. few polyps. very rare after 40 yrs.
74
What is Trans Lesion Synthesis
DNA damage that can be tolerated and bypassed during replication. replisome switches DNA Pol to one that "guesses" what base to insert. Cancer cells love it.
75
spontaneous abortions are caused by
60% defects, 40% normal. our of the 60 nearly half are trisomy.
76
Trisomy 21
Downs. 1/800 Live births. mainly nonfamilial. simian creases (not called that but i cant remember otherwise), upslant palpebral fissures, heart disease, otitis media, hypothyroidism. mostly nondisjunction. can also occur from robertsonian translocation
77
How does maternal age affect risk of abnormality
``` 1/1215= Age 15 1/5= Age 50 ```
78
Trisomy 18
Edwards. short sternum. digit abnormalities. round head. posterior rotation of ears. low hairline. high nasal bridge. semi-lethal= 10% survival rate past year 1.
79
Trisomy 13
Patau. Holoprosencephaly. heart defects (VSD). cleft lip/ palate. microcephaly. rocker bottom feet.
80
5p
Cri-du-chat. Cat like cry due to hypotonia and laryngeal abnormalities. growth restriction. microcephaly. moderate to sever intellectual deficit .
81
22q11.1 deletion
May manifest as Digeorge or Velocardialfacial. facial dysmorphology, slow growth, cleft palate. may have heart problems like tetralogy of fallot or aortic arch interrupt
82
Turner syndrome
in females. loss of second x. short stature. may have edema or webbing (webneck).
83
Klinefelter
XXY. can also include multiple x variants although this leads to mental deficits. normally found after Azospermia.
84
xxx,xyy
not syndromes typically. can have normal chromosomes
85
Williams (contiguous gene deletion syndrome)
puffy eyes, blue eyes, cocktail personality, aortic stenosis, hypercalcemia
86
WAGR
aniridia, wilms tumor, late onset kidney dysfunction, undescended testes
87
46, XY, female | 46,XX, male
-SRY mutations where the SRY gene usually found on the Y gene may abnormally crossover and create variants.

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