Clinical Cytogenetics Flashcards
What is a metacentric chromosome
P equals Q
What is a submetacentric chromosome
Q is greater than P
What is an acrocentric chromosome
Satellite/non-coding DNA is on the short arm
What type of chromosome has either two Ps or two Qs
Isochromosome
What does der stand for? Is it balanced or unbalanced
Derivative; unbalanced
What does mos stand for? What does that mean
Mosaic which is more than 1 cell type in the body
What does AT rich stain
Dark
What does CG rich stain
Light
What is high resolution banding
Arrest cells in prophase or early metaphase where they are more spread out so you can detect subtle abnormalities
What do fish probes detect
Thy target specific regions on specific chromosomes
What does Aneuvysion allow you to do
Rapidly analyze for trisomic chromosomes
What chromosomes are often trisomic
13,18,21
What does array CGH do
Picks up the smallest abnormality
Does array cgh detect balanced gene rearrangements
NO
What does a SNP demonstrate at every locus
Heterozygosity or homozygosity
What do regions of homozygosity indicate
Deletion, parents are related to one another/consanguinity/ recessive disorder… they may not have any clinical significance sometimes though
What is euploidy
Any cell that contains a multiple of 23 chromosomes
What splits in meiosis one
Homologs
What splits in meiosis 2
Sister chromatids
What is nondisjunction
Not splitting correctly which can lead to monosomy or trisomy
What are some features of there is excess paternal material in triploidy 21
Large placenta, small fetus, partial hydatidiform mole, oligohydramnios, syndactyly, congenital heart defects
What are some features of there is excess maternal material in triploidy 21
Small placenta, good fetal development, early loss
If someone is not mosaic in trisomy 21 what usually occurs
Neonatal death or loss of pregnancy
What are some clinical features of trisomy 21
Palmar crease, hypertelorism, upslanting eyes, midface hypoplasia, tongue thrust, congenital heart defects, moderate disability
Where may be a robertsonian translocation in Down syndrome patients between which two chromosomes
14 and 21
What arm of chromosome 14 is chromosome 21 attached to in trisomy 21 the robertsonian version
Q arm
What is trisomy 18 aka
Edward syndrome
What are some clinical features of trisomy 18
Clenched hands, overlapping fingers, rocker bottom feet, mental retardation, heart defects, small jaw, cleft lip, posterior rotation on ears
How long do ppl with trisomy 18 usually live
1 year
What is trisomy 13 aka
Patau syndrome
What are some clinical features of trisomy 13
Midline abnormalities, microencephaly, cleft lip, broad nasal bridge, low ears, intellectual disability
Do most ppl have a baby with trisomy 13 or do they miscarry
They miscarry
while most of the causes of nondisjunction are unknown, what are some of the risk factors?
hormone levels, smoking, radiation, thyroid disease, alcohol
what is the only known risk factor for nondisjunction
maternal age
is the extra X in Klinefelter syndrome maternally or paternally derived
maternally
is the extra X in triple X syndrome maternally or paternally derived
maternally
what are the clinical manifestations for klinefelter syndrome?
small testes, thin body, delayed secondary sex characteristics, gynecomastia, shy, normal IQ
what happens if a person has more than 3 X chromosomes
there will be problems
clinical symptoms of XXX?
little/no clinical symptoms, usually incidental finding, rarely have fertility or learning problems
clinical symptoms of XYY?
little/no symptoms, taller stature, minor learning problems
where is the genetic error in XYY?
paternal meiosis 2 error
what enhances survival in turner syndrome/ monosomy X/ 45X
being mosaic
clinical symptoms of turner syndrome/monosomy X?
short stature, infertility, neck webbing, normal IQ, some have heart and lymphatic problems at birth
what is monosomy X aka?
turner syndrome, 45X
is there a maternal age effect in turner syndrome
NO
if a female has short stature, they should get a karyotype… what would genetic counselors look for?
turner syndrome
what chromosome is the deletion on in williams syndrome
7
what is another name for Phelan McDermid Syndrome
22q13 deletion syndrome
clinical symptoms of phenal mcdermid syndrome/22q13 deletion syndrome?
hypotonia, developmental delay, little/ no speech, larger body size
Clinical symptoms of Williams syndrome
Raspy voice, intellectual disability, cocktail personality, heart problems, hypercalcemia, starburst pattern on irises, weakness in visual spatial construction
What is uniparental disomy
When one parent gives two chromosomes
What causes uniparental disomy
Trisomic rescue, mitotic error
What is isodisomy
2 copies of the same homolog
What is isodisomy an error of
Meiosis 2 or mitotic
What type of uniparental disomy increases your risk for recessive disease
Isodisomy
What is heterodisomy
One copy of each homolog from one parent
What is heterodisomy an error of
Meiosis 1
Is heterodisomy more common in paternal or material related nondisjunction
Maternal
Telomeres
Repeated information at the end of a chromosome that protects genes
What is the Philadelphia chromosome
Reciprocal translocation between chromosome 9 and 22
What are quadrivalents
Pairing of translocation products
What are the types of quadrivalents
Alternate (1 balanced and 1 normal) or adjacent (2 unbalanced)
What is robertsonian translocation
Translocation between 2 acrocentric chromosomes that results in a dicentric chromosome
What are the 5 acrocentric chromosomes in the human body
13,14,15,21,22
What part of the chromosome is lost in robertsonian translocation
Short arm of both chromosomes
What does an acrocentric chromosome have
Satellite DNA on the short arms
What is CATCH 22
CV abnormalities Abnormal facies T cell abnormalities Cleft palate Hypocalcemia
Do ppl with catch 22 have developmental delay/learning disabilities
Yes
What is wrong with the karyotype in catch 22
Submicroscopic deletion in 22q11.2
True or false. Most cases are de novo in catch 22
True
What disorder do ppl have velopharyngeal insufficiencies like a really nasally voice
Catch 22
What kind of abnormal facies do ppl with catch 22 have
Hypertelorism, prominent ears and nasal root, small mouth, micrognathia (small jaw)
What are ring chromosomes
Deletions of both ends of the chromosomes so they fuse together
Are ring chromosomes usually mosaic
Yes
Do paracentric inversions involve the centromere
No
Do pericentric inversions involve the centromere
Yes
How many centromeres Do the unbalanced products in paracentric inversions
Either 2 or 0
Are liveborns transmittedbalanced or unbalanced Products in paracentric inversions
Balanced
What type of inversion has a higher risk of infertility? Why?
Paracentric because of the invisible gametes
What are isochromosomes
Two copies of one arm and none of the other due to incorrect axis separation
What chromosomes are isochromosomes lethal in? What are they viable one?
Lethal in autosomes
Viable in sex chromosomes
What do features of rare chromosome abnormalities depend on
What chromosomes are involved and how much genetic material is missing or added
If patients have a rare chromosome abnormality what are they diagnosed with
Where chromosome abnormality
What is the management for rare chromosome abnormalities
Early intervention because they have a high risk for developmental disability
