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Medical Genetics
8.24 by Dr. McGoey at 8:30am
61
Pathology
Professional
08/24/2011

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Cards

Term
What is the lifetime frequency of genetic diseases?
Definition
670/1000
Term
What percent of people under 25 have 'genetic disease'?
Definition
5%
Term
How many abnormal genes does the average person have?
Definition
5-8 abnormal genes
Term
What are the three different classifications of genetic disorders?
Definition
chromosomal, single gene (mendelian inheritance and nontraditional inheritance), and complex multigenic/multifactorial
Term
What is the #1 known cause of 1st trimester miscarriages?
Definition
chromosomal/cytogenic abnormalities
Term
What percent of the population has a chromosomal abnormality?
Definition
1%
Term
How many 1st trimester abortions, stillbirths, and live births have a chromosomal abnormality?
Definition
60% of 1st trimester SAB, 6% of stillbirths, .6% of livebirths
Term
What are G-bands?
Definition
dark strips on chromosomes in a karytype caused by Geimsa stain
Term
What are indications for cytogenetic studies?
Definition
birth defects/malformations, stillborn neonate/spontaneous abortus, AMA, both parents in a couple with > 2 pregnancy losses, unbalanced chromosomes for both parents, tumors
Term
What are the two types of structural abnormalities?
Definition
1) balanced rearrangement- correct amount of genetic material but rearranged. Phenotype is normal.
2) unbalanced: loss/gain of genetic material. Phenotype is abnormal.
Term
Name examples of balanced cytogenetic disorders.
Definition
translocations, inversions
Term
What are some examples of unbalanced cytogenetic disorders?
Definition
translocations, deletions, duplications, isochromosome
Term
Describe the two types of translocations.
Definition
1)reciprocal- translocation between 2 chromosomes. Can be balanced or unbalanced.
2) robertsonian: a fusion of two acrocentric chromosomes. Can be balanced or unbalanced
Term
What is the incidence of reciprocal translocation?
Definition
1/500
Term
What is the incidence of Robertsonian translocation?
Definition
less common 1/900
Term
Which chromosomes are acrocentric and thereby can undergo Robertsonian tranlocations?
Definition
13-15; 21-22
Term
What are the two types of inversions?
Definition
paracentric: involves one arm of the chromosomes
pericentric: involves both arms of the chromosome
Term
A ring chromosome is due to what type of mutation?
Definition
a deletion
Term
What is the frequency of deletion mutations?
Definition
1/7000
Term
What is the incidence of deGeorge syndrome?
Definition
1/3000
Term
What are the symptoms of diGeorge syndrome and where is the deletion?
Definition
C: cardiac (TOF, TA)
A: abnormal face
T: thymus aplasia
C: cleft palate
H: hypocalcemia
22: deletion of 22q
Term
What/where is the mutation that causes Cri du Chat?
Definition
deletion on 5p
Term
T/F A few signs of Cri du Chat are epicanthal folds, mental retardation, and a heart defect.
Definition
True! also, the high pitched cry, hypertelorism, and microcephaly
Term
T/F Duplications are more harmful than deletions.
Definition
False, the opposite is true
Term
What is an Isochromosome?
Definition
loss of one arm of chromosome with duplication of the other arm
Term
What percent of Turner's is due to an Isochromosome?
Definition
15%
Term
What do you call a cell that has just 1 or 2 extra or missing chromosomes?
Definition
anueploidy
Term
What do you call it when a cell has chromosome numbers that are mutliples of the haploid number of chromosome (like 3n or 4n, instead of the normal 2n)?
Definition
polyploidy
Term
What causes Triploidy? What is the incidence of livebirths with triploidy?
Definition
dispermy
1/10,000
Term
T/F Down syndrome patients are at a lower risk for Alzhiemer's.
Definition
false, higher risk
Term
Which cancer are Down's syndrome patients at a higher risk for?
Definition
ALL (acute lymphoblastic leukemia)
Term
T/F Down's syndrome is the #1 cause of mental retardation.
Definition
False, Down's syndrome is the #1 cause of GENETIC mental retardation. Most MR is idiopathic.
Term
What genetic mutations cause down's?
Definition
95% is due to Trisomy 21
3% is due to unbalanced translocations
Term
What's your risk of having a Down's syndrome baby at 35? 40? 50?
Definition
35-.5%
40-1%
50-5%
Term
What percent of Down's syndrome patients have heart defects?
Definition
40%
Term
What are the symtoms of trisomy 18 (Edwards Syndrome)?
Definition
heand clench, omphalocele, heart defect, mental retardation, rocker bottom feet, horseshoe kidneys, death by 1 yoa
Term
What's the incidence of Edwards?
Definition
1/8000
Term
T/F The risk for ALL aneuploidies incresaes with maternal age.
Definition
true
Term
What are the symptoms of Trisomy 13 (Patau Syndrome)?
Definition
midline defects (cyclopia, heart defects, holoprosencephaly, cleft lip, neural tube defects, cutis aplasia), post axial polydactyly and death by 1 yr
Term
What is the incidence of Patau?
Definition
1/15,000
Term
What are the characteristics of Turner's syndrome?
Definition
short stature, webbed neck, shield chest, increased cubitus carrying angle, streak ovaries, coarctation of aorta, infertility with primary amenorrhea
Term
What are the characteristics of klinefelter's (XXY)?
Definition
tall, thin, delayed secondary sexual development, hypogonadism, infertility (decreased testosterone), gynecomastia
Term
What is the incidence of Klinefelter's?
Definition
1/850 livebirth males
Term
Describe XYY syndrome characteristics.
Definition
tall stature, increased behavioral problems
Term
What causes XYY? XXX?
Definition
XYY: paternal meitoic nondisjunction
XXX: maternal meiotic nondisjunction
Term
What are the features of XXX syndrome?
Definition
increased behavioral/learning problems
Term
What % of the pediatric and adult population have multifactorial conditions?
Definition
10% of pediatric population
60% of adult population
Term
For a multifactorial condition, the % contribution from genetics is termed ____.
Definition
heritability
Term
T/F Phenotypic traits, like height, IQ, and blood pressure, are multifactorial conditions.
Definition
true, observed in populations as unimodal, normally distributed, gaussian curves
Term
Multifactorial conditions that are either present or absent are termed ___.
Definition
discontinuous or discrete
Term
What are the two broad categories that multifactorial disorders are broken up into?
Definition
common adult diseases (diabetes, obesity, schizophrenia, CAD) and congenital malformations
Term
What 5 types of congenital malformations are classic multifactorial disorders?
Definition
congenital heart disease, cleft lip/palate, club foot, congenital hip dislocation, pyloric stenosis
Term
Because multifactorial conditions are a genetic category of exclusion, what must you look at/rule out to make sure it is a MF condition?
Definition
inheritance pattern is not Mendelian, cytogenetics are normal and disorder is isolated (non-syndromic)
Term
Recurrence Risks in multifactorial disorders can vary with...
Definition
severity of disease, sex of affected proband, and number of affected individuals in a family
Term
Incidence of Hypertrophic pyloric stenosis?
Definition
1/500 births, higher incidence in first born and males> females (5:1)
Term
What's the incidence of NTDs in the US?
Definition
1/1000
Term
What's the incidence of cleft palate? cleft lip and palate?
Definition
1/2000 cleft palate
cleft lip and cleft palate is 1/1000
Term
Which populations are at higher risk for cleft lip and palate?
Definition
native americans>asians>caucasians
males> females (3:2)
Term
What's the incidence of mild congenital heart disease? moderate-severe congenital heart disease?
Definition
1/20. 1/800
Term
What environmental factor can cause congenital heart disease?
Definition
maternal diabetes
Term
What are the recurrence rates for parents who have 1 child with an MF disorder? 2 children? 3 children? 4 children?
Definition
3-5%, 5-10%, 10-20%, and 20-40%
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