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