Genetics Flashcards
What is the clinical presentation of Prader-Wili syndrome?
Hyperphagia, obesity, small hands and feet, hypogonadism
What is the genetic cause of Prader-Willi syndrome?
4Mb deletion on chromosome 15q from PAPA
What is the clinical presentation of Angelman syndrome?
spontaneous, uncontrolled laughter, ataxia, and severe intellectual disability?
What is the genetic cause of Angelman syndrome?
a 4Mb deletion on chromosome 15q from MAMA
What is uniparental disomy?
two copies of a chromosome inherited from one parent
What is the clinical presentation of Beckwith-Wiedemann syndrome?
Large size for gestational age, large tongue, increased incidence of wilms tumor
What is the genetic cause of Beckwith-Wiedemann syndrome?
Imprinting on chromsome 11p; contains IGF2 gene, with 2 copies from father (normally father provides one copy; none from mother)
What is the clinical presentation and genetic cause of Silver-Russell syndrome
Growth retardation and short stature; deficient IGF2
What are a major pro and con for a conventional gene karyotype?
PRO: Genome-wide; numerical & structural
CON: 5-10Mb resolution
What are clinical presentations of Edward’s syndrome?
rocker-bottom feet, severe CNS impairment, horshoe kidneys, low and rotated ears
What is the genetic cause of Edward’s syndrome?
Trisomy 18
What are clinical presentations of Patau syndrome?
polydactyly, omphalocele, possibly holoprosencephaly or cleft palate
What is the genetic cause of Patau syndrome?
trisomy 13
What are clinical presentations of Cri-du-chat syndrome?
cry sounds like a cat, facial anomalies, severely low IQ (around 30)
What is the genetic cause of Cri-du-chat syndrome?
deletion in chromsome 5p
What are a major pro and con for FISH?
PRO: Resolution better than karyotype (smaller deletions & duplications detectable)
PRO: can be done on interphase chromosomes
CON: Limited to regions by tagged probes (NOT genome wide)
What are a major pro and con of Comparative Genomic Hybridization?
PRO: Good at detecting deletions and duplications
CON: Done with metaphase chromosomes, resulotion not excellent
What are major pros and cons of Cytogenetic Microarrays?
How much DNA is shared by dizygotic twins?
50%
A heritability score close to 1 indicated what?
Mostly genetically influenced
How is heritability calculated?
Understand the difference between fetal genetic testing
What is an example of an indirect genetic test?
linked marker polymorphism; not exact, but can traces patterns of inheritance through family members
Understand the differences between types of genetic tests
Define incomplete penetrance:
Some individuals with a disease-predisposing genotype do NOT develop disease phenotype
Which disease characterized by CAG repeats as well as age-dependent penetrance is notable for a progerssive loss of motor control (chorea)?
Huntington disease
What is the major difference between incomplete penetrance and variable expression?
IP: binary; phenotype is presence or absent
VE: variability in severity of a disease or trait
What type of genetic disease are Hemophilia A and Hemophilia B characterized as?
X-linked recessive
What clotting factor deficiency is associated with Hemophilia A?
Factor VIII deficiency
What clotting factor deficiency is associated with Hemophilia B?
Factor IX deficiency
Proximal limb wasting with pseudohypertrophy presenting in distal limbs may indicate what X-linked recessive disease?
Duchenne muscular dystrophy
Duchenne muscular dystrophy is typically caused by what types of mutations?
Frameshift (dystrophin is absent)
Becker muscular dystrophy is typically caused by what types of mutations?
In-frame (dystrophin is present but abnormal)
