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Flashcards in Genetics Deck (26):
1

variable expressivity

phenotype varies among individuals with the same genotype (different disease severity)

2

incomplete penetrance

not all individuals with a mutant gene show mutant phenotype

3

pleiotropy

one gene contributes to multiple phenotypic effects

4

mosaicism

presence of genetically distinct cell lines in the same individual, arises from mitotic errors after fertilization

5

heteroplasmy

presence of both normal and mutated mtDNA, resulting in variable expression of mitochondrial inherited disease

6

uniparental disomy

offspring gets 2 copies of a chromosome from 1 parent (heterodisomy is a meiosis 1 error, isodisomy is a meiosis II error)

7

imprinting

epigenetic process involving methylation - gene is silenced without a change in sequence

8

Prader-Willi syndrome

maternal imprinting: gene from mom is normally silent and Paternal gene is deleted/mutated
-- leads to hyperphagia, obesity, intellectual disability, hypogonadism, and hypotonia
-- Prader Willi is Paternal

9

Angelman syndrome

paternal imprinting: gene from dad is usually silent and Maternal gene is mutated/deleted
-- inappropriate laughter, seizures, ataxia, and severe intellectual disability
- angelMan has Maternal mutation

10

Autosomal Dominant Polycystic Kidney Disease

- adult onset, autosomal dominant
- bilateral, massively enlarged kidneys due to large cysts
- 85% due to PKD1 mutation on Chromosome 16

11

FAP

- autosomal dominant
- APC gene mutation leading to multiple colonic polyps that will progress to cancer if colon is not removed
- on chromosome 5

12

hereditary hemorrhagic telangiectasia

- AD inherited disorder of blood vessels
- telangiectasias, recurrent epistaxis, skin discolorations, AVMs, GI bleeding, hematuria
- aka Osler-Weber-Rendu

13

Hungtington disease

- AD disease with CAG repeat on chromosome 4
- depression, progressive dementia, choreiform movements, caudate atrophy, decreased GABA and Ach

14

NF1

- AD disorder with 100% penetrance, variable expression
- mutation in NF1 gene on chromosome 17 leads to cafe-au-lait spots and cutaneous neurofibromas

15

NF2

- AD disorder with NF2 mutation on chromosome 22
- bilateral acoustic schwannomas, juvenile cataracts, meningiomas, and ependymomas

16

von Hippel-Lindau disease

- AD disorder with numerous benign and malignant tumors
- deletion of VHL gene (tumor suppressor) on chromosome 3

17

chromosome mutations of autosomal dominant disorders

3- VHL
4- huntington
5- FAP

16- ADPKD
17- NF1
22- NF2

18

Duchenne muscular dystrophy

- x linked frameshift mutation in dystrophin gene
- onset before 5 years, dilated cardiomyopathy
- increased CPK and aldolase
- confirm diagnosis with western blot and muscle biopsy

19

Becker muscular dystrophy

- point mutation in dystrophin gene
- adolescent onset, less severe than Duchenne

20

myotonic type 1 muscular dystrophy

- CTG trinucleotide repeat expansion in DMPK gene --> abnormal expression of myotin protein kinase --> myotonia, muscle wasting, frontal balding, cataracts, testicular atrophy and arrhythmia

21

Fragile X

- x linked defect affecting methylation and expression of FMR1 gene (CGG repeat)
- post-pubertal macroorchidism, long face with large jaw, large everted ears, autism, mitral valve prolapse
- Fragile X = Xtra large testes, jaw and ears

22

Autosomal trisomies

- Downs (21-Drinking age) - duodenal atresia, hirschsprung, ostium primum ASDs, increased bHCG
- Edwards (18-Election age) - low set Ears, prominent occiput, clenched hands, decreased bHCG
-Patau syndrome (13-Puberty) - microcephaly, cleft lip/palate, holoprosencephaly, polydactyly
- common to all - decreased PAPP-A, increased nuchal translucency, intellectual disability, congenital heart disease,

23

Robertsonian translocation

nonreciprocal chromosomal translocation that occurs when long arms of 2 acrocentric chromosomes fuse at the centromere and the 2 short arms are lost

24

Cru-du-chat syndrome

congenital microdeletion of 5p (short arm)
- microcephaly, mod-severe intellectual disability, high-pitched cry, epicanthal folds, VSD

25

Williams syndrome

congenital microdeletion of long arm of chromosome 7 (7q), which includes elastin gene
- distinctive "elfin" facies, intellectual disability, hypercalcemia, well developed verbal skills and friendliness with strangers, CV probs

26

22q11 deletion sydromes

CATCH-22
- Cleft palate, Abnormal facies, Thymic aplasia (T cell deficiency), Cardiac defects, Hypocalcemia 2/2 parathyroid aplasia
- Di George - thymic, parathyroid and cardiac defects
-Velocardiofacial syndrome - palate, facial and CV defects