Shared Flashcard Set

Details

Medical Genetics
USMLE
126
Other
Graduate
04/29/2010

Additional Other Flashcards

 


 

Cards

Term
What type of mutation creates a new amino acid in place of a previous one?
Definition
missense
Term
What type of mutation changes the codon to a stop codon?
Definition
nonsense
Term
What gene is responsible for X inactivation?
Definition
XIST
Term
What is the proband?
Definition
the individual first effected by the disease
Term
What is allelic heterogeneity?
Definition
different mutations in the same locus that cause a variety of expression severity between families not within the same family
Term
What is the main difference between genetic drift and natural selection?
Definition
genetic drift is random whereas natural selection is not
Term
What is gene flow?
Definition
the movement of genes between popluations making the two populations more similar
Term
What does G-banding allow one to do?
Definition
visualize the chromosomes
Term
What are the steps in G-banding? (2)
Definition

trypsin digestion

Giemsa staining of bands

Term

What chromosome and what mechanism causes the mutation in Cri-du-chat and Williams syndrome?

 

How would you test for this type of mutation?

Definition

Cri-du-chat is ch. 5

Williams is ch. 7

 

BOTH ARE MICRODELETIONS

 

TEST w/ FISH

Term

What are the acrocentric chromosomes (5)?

 

What type of translocation can occur with them?

Definition

13, 14, 15, 21, 22

 

robertsonian translocation

Term
Explain the mechanism of robertsonian translocation?
Definition
two acrocentric chromosomes lose their short arms and subsequently the long arms join together. 
Term
What are the tips of the chromosomes called?
Definition
telomers
Term
What is the mechanism behind Li-fraumeni syndrome?
Definition

mutation in the TP53 gene which codes for p53. 

 

loss of function

Term
How many hits does a gain of function mutation need?
Definition
1 hit
Term
What is the highest dizygotic concordance obtainable?  Why?
Definition
50% b/c this is the most genetic material the two twins can share
Term
What are the three possible combinations of amnion and chorion that can occur with monozygotic twins?
Definition

same amnion and chorion

 

seperate amnion and chorion

 

same chorion, seperate amnion

Term
What is the difference between variable number of tandem repeats and short tandem repeat polymorphisms, with regards to what they detect?
Definition

variable number of tandem repeats detect minisatellite repeats

 

short tandem repeat finds microsatellites (2-6bp)

Term
What percentage cutoff value defines if two genes are linked?
Definition
two genes are linked if they crossover together more than 50% of the time.
Term
What is linkage disequilibrium?
Definition
the tendency for alleles at two linked loci to crossover
Term
What method does indirect genetic testing use?
Definition
recombination analysis (genetic linkage)
Term

At what week is amniocentisis done?

 

At what week is chorionic villus sampling done?

Definition

16 weeks for amniocentisis

 

10-12 wks for chorionic villus sampling

Term
Why can chorionic villus sampling give false+/false- results?
Definition
placental mosaicism
Term
What are the three steps of PCR?
Definition

denature

anneal

elongation

Term
What enzyme is used in the elongation period of PCR that creates the elongation?
Definition
heat stable DNA polymerase
Term

What does southern blotting detect?

 

northern blotting?

 

Western blotting?

Definition

Southern-DNA

Northern-RNA

Western-protein

Term
Which blotting procedures use a DNA probe?
Definition
southern and northern
Term
Which blotting method uses an antibody to detect substrate?
Definition
western
Term
What are microarrays used to detect?
Definition
single nucleotide polymorphisms (SNP)
Term
What is the difference between cDNA and normal DNA that will eventually code for a protein?
Definition
the cDNA lacks introns
Term
Why when cloning are the DNA fragments inserted into a bacterial plasmid that is antibotic resistance?
Definition
so they can be selected for using an antibiotic medium to get rid of any bacteria that doesn't contain the DNA fragment
Term
What type of inheritance results in neither of the 2 alleles being dominant?
Definition
codominance
Term
What is the difference between variable expression and incomplete penetrance?
Definition

variable expression: have the genotype with varying phenotype

 

incomplete penetrance: some with the genotype will not express the phenotype at all

Term
What is the formula for determining penetrance?
Definition
# with pheotype/total # with genotype
Term
What is pleiotropy?  An example of a disease?
Definition

when one mutation has effects in several different organs

 

EX: Marfan (fibrilin gene in many locations) or PKU

Term

What does inprinting do?

 

Definition
methylates (SAM) an allele making it inactive
Term
What are two classic examples of imprinting and consequences of not inheriting the non-imprinted allele?
Definition
angleman and prader willi
Term
What chromosome is involved in Prader-willi and angleman syndrome?
Definition
ch. 15
Term
What is the mechanism of prader willi?
Definition

maternal allele on ch. 15 is methylated normally-->inactive

 

at the same time the paternal allele on ch.15 is deleted

 

-->no copy of allele on ch.15

Term
What is the mechanism of Angelman syndrome?
Definition

ch. 15 paternal allele is methylated-->inactive

 

but the active maternal allele is deleted

 

-->no active ch. 15 allele

Term
What type of diseases are affected by anticipation?
Definition
trinucleotide repeat disorders
Term
What are the four main trinucleotide repeat disorders?
Definition

Huntington's

Myotonic dytrophy

Fragile X

Fredrich's Ataxia

Term

What are the trinucleotide repeats in the following disorders?

 

Huntingtons

Myotonic Dystrophy

Fragile X

Friedrich's Ataxia

Definition

Huntingtons CAG

Myotonic CTG

Fragile X CGG

Freidrichs GAA

Term
What is loss of heterozygosity?
Definition

there is already an inheritied mutation on the locus causing heterozygote for the mutation

 

 

the loss of heterozygosity comes with a second hit resulting in full mutation

Term
Define locus heterogenity?
Definition
mutations at different loci producing same phenotype
Term
Name three disease examples of locus heterogenity?
Definition

Marfan

MEN 2B

Albinism

Term
What is heteroplasmy?
Definition

a mutation in mitochondrial DNA is only passed from mother to offspring.  Not all the mitochondria is mutated.

 

Heteroplasmy is the varying severity of phenotype depending on how much of the mutated mitochondrial DNA is passed on in relation to normal mitochondrial DNA

Term
What are three examples of diseases that show heteroplasmy?
Definition

mitochondrial encephalomyopathy

myoclonic epilepsy

lebex herditary optic neuropathy

Term
Why do mitochondrial DNA mutations only come from mother?
Definition
b/c sperm mitochondria are lost when sperm enters the egg
Term
What is uniparental disomy?
Definition
when the two chromosomes come from the same parent
Term
What is the mechanism of prader willi if the patient has two copies of maternal ch. 15? 
Definition

uniparental disomy

 

patient has both maternal copies which are imprinted and thus inactive

Term
What is the difference between transversion and transition?
Definition

Transversion is the substituation of a guanine for a thymine reside or vise versa

 

Transition is the substitutaion of a purine for another purine or a pyrimadine for another pyrimadine

Term
What is the Hardy Weinberg equation?
Definition
p2 + 2pq + q2 = 1
Term
What in the Hardy Weinberg equation represents carrier frequency?
Definition
2pq
Term
What disease presents secondary to an imprinting event and microdeletion with hypogonadism and hyperphagia?
Definition
Prader Willi
Term
What disease presents secondary to imprinting and microdeletion with inappropriate laughter and seizures?
Definition
angelman syndrome
Term
What are AR modes of inheritance usually a result of?
Definition
enzyme deficienies
Term
What are manifesting heterozygotes?
Definition
these are females who inherit an X-linked recessive disorder and subsequently inactivate more of the normal X causing mild phenotype
Term
How can heterozygotic females for an x-linked recessive disease manifest a pheotype?
Definition
manifesting heterozygotes: x inactivation of a greater proportion of normal X chromosomes
Term
In an x-linked dominant disorder, what percentage of daughters of affected fathers have the disorder?
Definition
all
Term

What disease causes degeneration of retinal ganglion cells and axons-->central vision loss?

 

What type of inheritance does it follow?

Definition

Leber's hereditary optic neuropathy

 

mitochondrial inheritance

Term
What protein is defective in achondroplasia?
Definition
FGF3 receptor
Term
What disorder of short stature is associated with advanced paternal age?
Definition
achondroplasia
Term
In AD-polycystic kidney disease what is true about the kidney (s) effected?
Definition
it is bilateral
Term
What chromosome when mutated produces ADPKD?
Definition
Ch. 16
Term
What three other disease is associated with ADPKD?
Definition

polycystic liver

mitral valve prolapse

berry aneurysm

Term
What AD disease has associated risk of berry aneurysm?
Definition
ADPKD
Term
What chromosome is mutated in familial adenomatous polyposis?
Definition
ch. 5
Term
What gene is deleted in familial adenomatous polyposis?
Definition
APC tumor supressor gene
Term
In familial hypercholesterolemia what is the genetic defect?
Definition
abnormal or absent LDL receptor
Term
How will heterozygotes for familial hypercholesterolemia present?
Definition
w/ eleveated cholesterol
Term
How will homozygotes for familial hypercholesterolemia present?
Definition
cholesterol very high with tendon xanthomas and MIs
Term
What disease presents with recurrent epitaxis, telangiectasia, skin discoloration, and AVMs?
Definition
Hereditary hemorrhagic telangiectasia (Osler Weber)
Term
What is the genetic defect in hereditary spherocytosis?
Definition
spectrin defect
Term
What is the cure for hereditary spherocytosis?
Definition
splenectomy
Term
What chromosome is the Huntington trinucleotide repeat found on?
Definition
ch. 4
Term
What mutation is often found in MEN2A and MEN2B?
Definition
ret gene
Term
What chromosome is mutated in NF1 and NF2 respectively?
Definition

NF1 17

NF2 22

Term
Which type of neurofibromatosis is associated with phenochromocytomas?
Definition
NF1
Term
What chromosome is associated with the mutation for VHL syndrome?
Definition
ch. 3
Term
What gene is deleted in von-hippel-lindau disease and what type of gene is it?
Definition
VHL tumor suprressor gene
Term
What gene is constituatively active due to mutation in VHL syndrome?  What is the result?
Definition
HIF transcription factor-->angiogenic growth
Term
What two disorders are very common in Ashkenazic Jews?
Definition

Tay Sachs

Gaucher's type I

Term
What disease presents in a child with red, scaled skin after exposure to sun due to lack of a DNA excision repair gene?
Definition
xeroderma pigmentosum
Term
What is in common between PKU, sickle cell anemia, thalassemia, and hemochromotosis?
Definition
they are all AR inheritance
Term
How is xeroderma pigmentosum inheritated?
Definition
AR
Term
Name 10 common x-linked recessive disorders?
Definition

bruton agammaglobulinemia

Wiskott Aldrich

fabry

G6PD deficiency

ocular albinism

lesch-Nyhan

Duchene/Beckers MD

Hunter's

Hemophilia A/B

Term
What chromosome is involved in the Cystic fibrosis mutation?
Definition
CH. 7
Term
What is the result of a deleted Phe amino acid at position 508 of ch. 7?
Definition

post translational abnormal protein folding-->cystic fibrosis

 

channel is degraded before reaching the membrane

Term
What two infections are common in cystic fibrosis patients?
Definition
psuedomonas and staph aureus
Term
How can you treat Cystic fibrosis medically to loosen mucous?
Definition
N-acetylcysteine
Term
What is the most common lethal genetic disease of caucasians?
Definition
cystic fibrosis
Term
What disease presents often with bilateral vas deferens agensis?
Definition
cystic fibrosis
Term
What is the MOA of N-acetylcysteine in treating cystic fibrosis?
Definition
cleaves disulfide bonds within mucous glycoproteins
Term
What is the genetic mutation mechanism in duchenne's muscular dystrophy?
Definition
frame shift mutation-->no dystrophin gene
Term
What is the longest known human gene?
Definition
dystrophin
Term
What does dystrophin do?
Definition
anchors muscle fibers
Term
What lab value and pathology specimen is needed to dx muscular dystrophy?
Definition

elevated CPK

muscle biopsy

Term
What X linked dominent disorder involves DNA chromosomal breakage?
Definition
fragile X
Term
Name three clinical manifestations of fragile X?
Definition

large testes

large jaw

large ears

Term
What are the first and second most common causes of genetic mental retardation?
Definition

1. Downs

2. Fragile X

Term
What heart condition is assoicated with Fragile X syndrome?
Definition
mitral valve prolapse
Term
What disorder can be diagnosised by putting DNA in a folate deficient bath or methotrexate followed by southern blot?
Definition
fragile X
Term
What are the three surviable trisomies with names and chromosome?
Definition

Down 21

Edwards' 18

Patau's 13

Term
What is the most common trisomy that results in miscarriage?
Definition
trisomy 16
Term
In addition to the three most common surviable trisomies what other trisomy disorder can survive b/c of increase in mosaicism?
Definition
trisomy 8
Term
What is the result of AFP, hCG, inhibin, and estriol screening during pregnancy in a patient with Downs?
Definition

AFP and estriol decreased

hCG and inhibin increased

 

Term
What will the ultrasound show in a Down's pregnancy?
Definition
nuchal transluscency
Term
What trisomy presents can present with duodonal atresia?
Definition
Downs
Term
What three diseases/disorders are down's patients at risk for?
Definition

Drinking age is 21--> may need AAA

 

Acute lymphoblastic leukemia

Atrial Septal Defect (and VSD)

Alzheimers at early age

 

Term
What are the three possible genetic ways an individual can acquire down's syndrome?
Definition

nondisjuction (95%)

robertsonian translocation (14 and 21) 4%

mosacism (1%)

Term
What is the mechanism of mosaicism causing Downs?
Definition
nondisjuction during an early mitosis
Term
What are the three main clinical findings in a patient with edwards syndrome?
Definition

election age is 18--> president J.F.K.

 

small jaw

overlapping fingers

clenched fingers (knuckles)

Term
What are the three main clinical presentations of Patau's syndrome?
Definition

puberty age is 13-->all have "P"

 

holoproencephaly

polydactyly

cleft palate

 

Term
What is the difference between pericentric and paracentric inversions?  Which can go through miosis?
Definition

pericentric includes the centromere and can go through miosis

 

paracentric doesn't include centromere and cannot go through meiosis

Term
What is the characteritis finding in Cri-du chat syndrome?
Definition
high pitch crying
Term
What disease presents with hypercalcemia due to senstivity to vit D, well developed verbal skills, and very friendly personality?
Definition
Williams syndrome
Term
What type of facie does a William's syndrome patient have?
Definition
Elf like
Term
What are the five clinical manifestations of the 22.q.11 deletion disorders?
Definition

CATCH 22

 

Cleft palate

abnormal facies

Thymic aplasia

carciac anomolies

hypocalcemia

Term
What is the main difference between DiGeorge Syndrome and Velocardiofacial syndrome?
Definition

DiGeorge invovles thymus and parathyroid problems

 

Velocardiofacial involves facial problems (palate)

Term
What is the translocation in CML and what results?
Definition
CML: (9:22)-->philadelphia chromosome-->platelet derived growth factor defect
Term
What is the translocation involved in AML?
Definition
(15:17)-->retinoic acid
Term
What translocation is involved in follicular lymphoma?
Definition
(14:18) Bcl2
Term
What translocation is involved in Burkitts lymphoma?
Definition
(8:14)-->c-myc
Term
What translocation is involved in mantle cell lymphoma?
Definition
(11:14)-->cyclin D
Term
What is the result of 15:17 translocation?
Definition
AML-->PML/RARa
Supporting users have an ad free experience!