USMLE 1 Genetics
Terms
undefined, object
copy deck
-
how many chromosomes and autosomes does each cell have?
what is the genetic term? -
46 chromosomes
22 pairs of autosomes
1 pair of sex chromosomes
"Diploid" -
Definition:
a chromosome number that is not a multiple of 23 (the normal haploid number) - Aneuploidy
- (2) ways that a haploid can become aneuploidy
-
Nondisjunction
(ex - Down's)
Anaphase Lag
(monosomy) -
what most commonly occurs w/ a polyploidy fetus?
give an example of what polyploidy means -
spontaneous abortion
Polyploidy = multiples of 23 chromosomes;
ex) 69 chromosomes in patient -
Definition:
two acrocentric chromosome are joined by common centromere causing the joining of the long arms (and possible loss of the short arms) - Robersonian Translocation
-
Definition:
the normal inactivation of one X chromosome -
Lyonization
(creation of Barr Body) -
How many Barr Bodies:
1. XX
2. XY
3. XXXY -
XX = 1 barr body
XY = NO barr bodies
XXXY = 2 barr bodies -
Definition:
when the cells in the body have a different genetic make-up (such as random X inactivation in females) - Mosaicism
-
Dx:
large forehead, broad nasal bridge, epicanthal folds, Brushfield spots, simian crease
genetic problem? -
Down's syndrome
(Trisomy 21) -
MCC of Down's syndrome
what is the other cause?
what is the "Familial form"? -
Nondisjunction
(Robertsonian) Translocation
(familial form) -
MC heart defect w/ Down's syndrome
what is it due to? -
Septum primum-type ASD
due to: Endocardial Cushion defect - (3) MC complications of Down's syndrome
-
AAA:
ASD
ALL
Alzheimers -
what is the maternal screening for Down's:
1. Alpha-fetoprotein
2. hCG
3. Unconjugated estriol -
AFP = Low
hCG = High
E2 = Low -
Dx:
severe mental retardation, microcephaly, wide-set eyes, low birth weight, round face, unusual cry
genetic problem? -
Cri du chat
(deletion: 5p-) -
Dx:
cardiac abnormalities, hypocalcemia, thymic aplasia, abnormal facies, cleft palate
genetic problem? -
DiGeorge syndrome
(also called Velocardialfacial synd)
(22q11 microdeletion)
*signs = CATCH-22 -
Dx:
mental retardation, prominent occiput, Micrognathia, Rocker-bottom feet, index finger overlaps 3rd and 4th fingers, Congenital heart dz
genetic problem? -
Edwards syndrome
(Trisomy 18 - nondisjunction)
*18 = Election = Edwards -
Dx:
mental retardation, microcephaly, Microphthalmia, cleft lip and palate, Polydactyly, rocker-bottom feet
genetic problem? -
Patau syndrome
(Trisomy 13 - nondisjunction)
13 = Puberty = Patau (= 13 fingers) -
Definition:
disorder when there are at least two X-chromosomes and one or more Y-chromosomes - Klinefelter syndrome
-
Dx:
male w/ Atrophic testes, Tall stature, Gynecomastia, decreased testosterone, increased pituitary gonadotropins, male infertility
genetic problem? -
Klinefelter syndrome
(maternal meiotic nondisjunction)
[Kline felt her TAG him] -
Dx:
Violent behavior, tall, severe Acne - XYY syndrome
- MCC of Primary Amenorrhea
- Turner's syndrome
-
Dx:
Short stature, shield-like chest, Amenorrhea, Webbed neck, Ovary replaced by Fibrous Streaks
genetic problem? -
Turner's syndrome
(XO w/o Barr bodies)
[Turner WAS not feminine] - MC cardiac problem w/ Turner's syndrome
- Coarctation of the aorta
- (2) common cardiac defects w/ 22q11 syndromes (DiGeorge)
-
Truncus Arteriosus
Tetralogy of Fallot
[where all the T's went to...] -
Dx:
mental retardation, long face w/ large jaw, large everted ears, Autism, Macro-orchidism
genetic problem? -
Fragile X syndrome
(X-lined defect w/ CGG repeats)
[big testicles = X-rated] -
what is the underlying (biochemical) cause of Fragile X syndrome?
what is unusual about this syndrome? -
defect in Methylation of FMR1 gene
X-linked problem that may show signs of retardation in male and female offspring -
Definition:
severity of Dz worsens or age of onset of dz is earlier in succeeding generations
(example) -
Anticipation
(Huntingtons) -
Definition:
hereditary disorders in which differing phenotypes occur depending on whether an abnormal gene is of maternal or paternal origin
(examples) -
Genomic Imprinting
(Prader-Willi or Angelman) -
Dx:
mental retardation, hypogonadism, hypotonia, behavior problems, uncontrolled appetitie leading to obesity and DM
genetic problem? -
Prader-Willi syndrome
(5q11-13 deletion on father's chromosome) -
Dx:
mental retardation, ataxia, seizures, inappropriate laughter
genetic problem? -
Angelman syndrome
(5q11-13 deletion on mother's chromosome) -
Definition:
Not all individuals w/ mutant genotype show mutant phenotype - Incomplete penetrance
-
Definition:
one gene has greater then one effect on the individual's phenotype - Pleiotropy
-
Definition:
a heterozygote produces a nonfunctional altered protein that also prevents the normal gene product from functioning -
Dominant Negative mutation
(exerts a Dominant effect) -
Definition:
mutations at different loci can produce the same phenotype
(example) -
Locus Heterogenicity
(Albinism) -
Equation for Hardy-Weinberg population genetics:
Disease Prevalence - p^2 + 2pq + q^2 = 1
-
Equation for Hardy-Weinberg population genetics:
Allele Prevalence - p + q = 1
-
Equation for Hardy-Weinberg population genetics:
Heterozygote Prevalence
(p and q on separate alleles) - HP = 2pq
-
type of inheritance:
often due to Structural defects - Autosomal Dominant
-
type of inheritance:
often due to Enzyme deficiencies - Autosomal Recessive
-
Main sign of:
X-linked Recessive - no male-to-male transmission
-
Main sign of:
X-linked Dominant - All females are affected by father
-
Lysosomal storage Dz:
peripheral neuropathy of hands and feet, angiokeratomas, CV and renal Dz
Enzyme?
inheritance? -
Fabry's Dz
(alpha-Galactosidase A)
X-recessive -
Lysosomal storage Dz:
hepatosplenomegaly, aseptic necrosis of femur, bone pain, unique macros
Enzyme? -
Gaucher's Dz
(Glucocerebrosidase) -
Lysosomal storage Dz:
progressive neurodegeneration, hepatosplenomegaly, cherry-spot on macula
Enzyme? -
Niemann-Pick
(Sphingomyelinase) -
Lysosomal storage Dz:
progressive neurodegeneration, developmental delay, cherry-spot macula, lysozymes w/ onion skin
Enzyme? -
Tay-Sachs Dz
(Hexosaminidase A) -
Lysosomal storage Dz:
peripheral neuropathy, developmental delay, optic atrophy
Enzyme? -
Krabbe's Dz
(beta-Galactosidase)
[Krabs have small eyes] -
Lysosomal storage Dz:
developmental delay, gargoylism, airway obstruction, corneal clouding
Enzyme? -
Hurler's syndrome
(Alpha-L-IDuronidase)
[A Lit-ID in Quasimoto caused him to HURL the GARGOYLE] -
Lysosomal storage Dz:
mild developmental delay, mild gargoylism, airway obstruction, aggressive behavior
Enzyme?
inheritance? -
Hunter's syndrome
(Iduronate Sulfatase)
[Hunter's Aggressive ID Shot the X]
X-recessive -
Familial Dyslipidemia type:
Inc Chylomicrons only
pathology? -
Type I
(hyperchylomiconemia)
Lipoprotein Lipase deficiency -
Familial Dyslipidemia type:
Increased LDL only
(high blood cholesterol)
pathology? -
Type IIa
(hypercholesterolemia)
Low LDL receptors -
Familial Dyslipidemia type:
Increased LDL and VLDL
pathology? -
Type IIb
(combined hyperlipidemia)
Hepatic overproduction of LDL -
Familial Dyslipidemia type:
Increased IDL, VLDL
pathology? -
Type III
(dysbetalipoproteinemia)
Altered Apo-E -
Familial Dyslipidemia type:
Increased VLDL only
(high blood TG)
pathology? -
Type IV
(hypertriglyceridemia)
Hepatic overproduction of VLDL -
Familial Dyslipidemia type:
Increased VLDL, chylomicrons
pathology? -
Type V
(mixed hypertriglyceridemia)
Inc production or Dec clearance of VLDL and chylomicrons -
Autosomal Dominant Dz:
cafe-au-lait spots, neural tumors, pigmented iris hamartomas, scoliosis -
Neurofibromatosis Type 1
(Von Recklinghausen Dz)
(chrom 17) -
Autosomal Dominant Dz:
bilateral acoustic neuromas, optic pathway gliomas, juvenile cataracts -
Neurofibromatosis Type 2
(chrom 22) -
Autosomal Dominant Dz:
facial lesions, hypopigmented "ash leaf spot" on skin, cortical and retinal hamartomas, seizures, mental retardation - Tuberosus Sclerosis