Genetics Flashcards
blood groups & alpha1 anti trypsin deficiency demonstrate what type of genetics?
codominance- both alleles contribute to phenotype of heterozygote
neurofibromatosis type 1 genetics
variable expressivity- phenotype varies among ppl with same genotype
untreated phenylketonuria genetics with light skin, intellect disability, musty body odor
pleiotropy- one gene causes multiple phenotypic effects
tendency for certain alleles at 2 linked loci to occur together more/less often than expected by chance; measured in a pop. (not family)
linkage disequilibrium
genetically distinct cell lines in same person
mosaicism
somatic mosaicism- mutation arises from mitotic errors after fertiliz & propogates thru many tissues/organs
gonadal mosaicism- mutation only in egg/sperm cells
mutation affecting G protein signaling - unilat cafe au lait spots, polyostotic fibrous dysplasia, precocious puberty, mult endocrine abnormalities
lethal if mutation occurs before fertil (affects all cells)
survivable in those with mosaicism
McCune Albright Syndrome
mutations at different loci can produce similar phenotype
ie. albinism
locus heterogeneity
different mutations in same locus produce same phenotype
ie. beta thalassemia
allelic heterogeneity
presence of both normal & mutated mito DNA causing variable expression in mito inherited disease
heteroplasmy
offspring receives 2 copies of chrom from 1 parent and no copies from the other parent
uniparental disomy
heterodisomy- heterozygous, meiosis I error
isodisomy- homozygous, meiosis II error, postzygotic
consider when person manifests with recessive disorder but only 1 parent is a carrier
only 1 active allele at some loci with the other inactive d/t methylation - once the other active allele is deleted it leads to disease
imprinting
maternal imprinting: maternal gene is normally silent + parental gene is deleted/mutated on chrom 15 - hyperphagia, obesity, intellect disability, hypogonadism, hypotonia
may be a result of maternal uniparental disomy w/ both maternal genes imprinted
Prader Wili Syndrome
^p stands for paternal gene deletion
paternal imprinting: paternal gene normally silent + maternal gene deleted/mutated on chrom 15 - inappropriate laughter, sz, ataxia, severe intellect disability
may be result of paternal uniparental disomy w/ both paternal genes imprinted
angelMan syndrome
^m stands for maternal gene deletion
often due to defects in structural genes, many generations affected, M & F
autosomal dominant
often due to enzyme deficiencies, usually in only 1 generation, more severe, present in childhood usually
autosomal recessive
sons of heterozygous mothers have 50% chance of being affected, no male to male transmission, skips generations, more severe in males, females homozygous to be affected
X linked recessive
transmitted thru both parents, mom transmits to 50% of daughters & sons, dad transmits to all daughters but no sons
X linked dominant
inherited X linked dominant disorder with increase in phosphate wasting at PCT causing rickets-like presentation
Hypophosphatemic rickets
rare disorder of mito inheritance 2’ to failure in oxidative phosphorylation
with myopathy, lactic acidosis, CNS disease, ragged red fibers on muscle biopsy
mitochondrial myopathies
bilateral enlarged kidneys with many cysts
mutated PKD1 on chrom 16 or PKD2 on chrom 4
autosomal dominant polycystic kidney disease
‘16 letters in polycystic kidney’
adenomatous polyps in colon after puberty, mutated chrom 5q APC gene
Familial adenomatous polyposis
‘5 letters in polyp’
high LDL d/t defective/absent LDL receptor leads to severe atherosclerotic disease early, corneal arcus, tendon xanthomas (achilles esp.)
familial hypercholesterolemia
genetics of FAP
autosomal dominant
genetics of familial hypercholesterolemia
autosomal dominant
inherited disorder of blood vessels - telangiectasias, recurrent epistaxis, skin discoloration, AVM, GI bleeds, hematuria
Hereditary hemorrhagic telangiectasia/Osler Weber Rendu syndrome
genetics of hereditary hemorrhagic telangiectasia
autosomal dominant
spheroid erythrocytes d/t spectrin or ankyrin defect, hemolytic anemia, high MCHC, high RDW
hereditary spherocytosis
genetics of hereditary spherocytosis
autosomal dominant
depression, progressive dementia, choreiform, caudate atrophy, high DA, low GABA, low ACh
Huntington disease
genetics of Huntington’s - gene, chrom #, inheritance
autosomal dominant, anticipation
chrom 4 trinucleotide repeat CAG
multiple malignancies at early age
aka SBLA cancer syndrome: sarcoma, breast, leukemia, adrenal gland
Li Fraumeni syndrome
genetics of Li Fraumeni syndrome
abnormal TP53
autosomal dominant
defective fibrin (scaffold for elastin) - CT disorder of skeleton, heart, eyes - tall, long extremities, pectus excavatum, hypermobile, arachnodactyly, cystic medial necrosis of aorta, floppy mitral valve, subluxation of lens
marfan syndrome
genetics of marfan syndrome
FBN1 gene on chrom 15
autosomal dominant
several distinct syndromes w/ familial tumors of endocrine glands - pancreas, parathyroid, pituitary, thyroid, adrenal medulla
mutliple endocrine neoplasias (MEN1, 2A, 2B)
genetics of MEN
autosomal dominant
MEN1 gene
RET gene for MEN2A/B
neurocutaneous disorders w/ cafe au lait spots, cutaneous neurofibromatomas, optic gliomas, pheochromocytomas, lisch nodules (pigmented iris hamartomas)
neurofibromatosis type 1 (von Recklinghausen disease)
genetics of NF1
autosomal dominant
100% penetrance, variable expression
mutated NF1 gene on chrom 17 (‘17 letters in von Recklinghausen’)
bilateral acoustic schwannomas, juvenile cataracts, meningiomas, ependymomas
neurofibromatosis type 2
genetics of NF2
autosomal dominant
NF2 gene on chrom 22 (‘type 2 on chrom 22’)
neurocutaneous disorder w/ multi organ involvement with many benign hamartomas
tuberous sclerosis
genetics of tuberous sclerosis
autosomal dominant
incomplete penetrance, variable expression
many tumors (benign & malignant) assoc with deletion of VHL gene (tsg) on chrom 3
von Hippel Lindau disease
‘3 words for chrom 3’
genetics of von Hippel Lindau disease
autosomal dominant
genetics of albinism
autosomal recessive
genetics of autosomal recessive polycystic kidney disease
autosomal recessive
genetics of glycogen storage diseases
autosomal recessive
genetics of hemochromatosis
autosomal recessive
genetics of Kartagener syndrome
autosomal recessive
genetics of mucopolysaccharidoses (except for Hunter syndrome)
autosomal recessive
genetics of phenylketonuria
autosomal recessive
genetics of sickle cell anemia
autosomal recessive
genetics of sphingolipidoses (except Fabry disease)
autosomal recessive
genetics of thalassemias
autosomal recessive
genetics of wilson disease
autosomal recessive
genetics of cystic fibrosis
autosomal recessive
CFTR gene on chrom 7
usually deletion of Phe508
labs with cystic fibrosis
high Cl- conc (>60) in sweat
contraction alkalosis with hypokalemia
high immunoreactive trypsinogen in newborn
genetics of bruton agammaglobulinemia
x linked recessive
genetics of wiskott-aldrich syndrome
x linked recessive
genetics of fabry disease
x linked recessive
genetics of G6PD deficiency
x linked recessive
genetics of ocular albinism
x linked recessive
genetics of lesch-nyhan syndrome
x linked recessive
genetics of duchenne/becker muscular dystrophy
x linked recessive
genetics of hunter syndrome
x linked recessive
genetics of hemophilia A/B
x linked recessive
genetics of ornithine transcarbamylase deficiency
x linked recessive
muscular dystrophy d/t frameshift mutation causing truncated dystrophin protein - inhib muscle regeneration
Duchenne muscular dystrophy
weakness starts in pelvic girdle & rises, pseudohypertrophy of calf mm., gower maneuver, waddling gait, onset before 5yrs, dilated cardiomyopathy
Duchenne muscular dystrophy
largest protein coding human gene with high chance of spont mutation
dystrophin gene
labs of duchenne muscular dystrophy
high CPK & aldolase
confirm with western blot + muscle biopsy
muscular dystrophy d/t non frameshift mutation in dystrophin gene (partially functional), less severe, onset adolescence
Becker muscular dystrophy
CTG trinucleotide repeat expansion in DMPK gene - abnormal expression of myotonin protein kinase - myotonia, m. wasting, cataracts, testicular atrophy, frontal balding, arrhythmia
myotonic type 1 muscular dystrophy
genetics of myoclonic type 1 muscular dystrophy
autosomal dominant
genetics of fragile X syndrome
x linked
FMR1 gene, trinucleotide repeat CGG
muscular dystrophy w/ intellect disability, macroorchidism, long face, large jaw, large everted ears, autism, MVP
fragile x syndrome
CGG trinucleotide repeat
fragile x syndrome
GAA trinucleotide repeat
friedreich ataxia
CAG trinucleotide repeat
Huntington’s
CTG trinucleotide repeat
myotonic dystrophy
common assoc with down syndrome
duodenal atresia, Hirschsprung disease, ASD, brushfield spots, early onset Alzheimer’s, incr risk ALL & AML
which chrom codes for amyloid precursor protein
chrom 21 (Down syndrome chrom)
most common cause of trisomy 21
meiotic non disjunction assoc with AMA
rare genetic causes of trisomy 21
robertsonian translocation
mosaicism (post fertil mitotic error)
first trimester findings with trisomy 21
high nuchal translucency, hypoplastic nasal bone
low serum PAPP-A, high beta hCG
second trimester findings with trisomy 21
low AFP, high beta hCG, low estriol, high inhibin A
trisomy 18
Edwards syndrome
‘Election age 18’
severe intellect disability, rocker bottom feet, micrognathia, low set ears, clenched hands w/ overlapping fingers, prominent occiput, congenital heart disease
death within 1 yr
Edwards syndrome
labs for edwards syndrome
low PAPP-A, low beta hCG, low AFP, low estriol, low/normal inhibin A
trisomy 13
Patau syndrome
‘Puberty at 13’
intellect disability, rocker bottom feet, microphthalmia, microcephaly, cleft lip/palate, holoprosencephaly, polydactyly, congenital heart disease, cutis aplasia
Patau syndrome
labs of patau syndrome
low beta hCG, low PAPP-A, high nuchal translucency
disorders assoc with chrom 3
von hippel lindau disease
renal cell carcinoma
disorders assoc with chrom 4
ADPKD (PKD2)
Huntington’s
disorders assoc with chrom 5
Cri du chat syndrome
FAP
disorders assoc with chrom 7
Williams syndrome
cystic fibrosis
disorder assoc with chrom 9
Friedreich ataxia
disorder assoc with chrom 11
Wilms tumor
disorders assoc with chrom 13
Patau syndrome ('puberty') Wilson disease
disorders assoc with chrom 15
Prader-Willi syndrome
Angelman syndrome
disorder assoc with chrom 16
ADPKD (PKD1)
disorder assoc with chrom 17
Neurofibromatosis type 1
disorder assoc with chrom 18
Edwards syndrome
disorders assoc with chrom 22
Neurofibromatosis type 2 DiGeorge syndrome (22q11)
disorder assoc with X chrom
fragile X syndrome
X linked agammaglobulinemia
Klinefelter syndrome (XXY)
type of chrom translocation that commonly involves chrom 13, 14, 15, 21, 22
Robertsonian translocation
congenital microdeletion of short arm of chrom 5
microcephaly, intellect disability, high pitched crying, epicanthal folds, VSD
Cri du chat syndrome
congenital microdeletion of long arm chrom 7 (deletes elastin gene) - elfin facies, intellect disability, hyperCa, well develop verbal skills, extreme friendliness, CV problems
Williams syndrome
22q11 deletion syndromes
DiGeorge syndrome
Velocardiofacial syndrome
cause of 22q11 deletion
aberrant development of 3rd & 4th branchial pouches
cleft palate, abnormal facies, thymic aplasia, cardiac defects, hypoCa
22q11 syndrome