Chromosome disorders Flashcards
Who invented karyotype analysis and when?
Tijo and Levan in 1956
What causes mitosis?
Phytohemagglutinin
How do you stop cells in metaphase?
Colchicine and only gross morphology is visible
When was chromosome banding developed?
1970s
Why was the Giemsa stain developed?
To identify the plasmodium of malaria
After Gustav Giemsa’s death, with was added to advance karyotype techniques? What does it do?
G stain with trypsin on chromosomes. Banding allows one to identify major chromosome abnormalities
What does karyotype testing allow you to do?
A test to identify and evaluate the size, shape and number of chromosomes in sample cells
In a karyotype what are the dark areas and the light areas?
The dark areas are heterochromatin where the DNA that is condensed and not expressed. The light bands are euchromatin, the DNA that is expressed
What is an aneuploidy?
Loss or gain of 1 chromosome
What are the percentages of non-disjuction?
90% = maternal, 5% = paternal, 4% robertsonian translocation, 1 mosaicism
What is a monosomy? What is the only viable monosomy?
Loss of one chromosome. The only viable monosomy is X0.
What is a trisomy? Autosome examples? Sex chromosome examples?
Gain of a chromosome. 21/18/13 and XXY, XXX, XYY
What causes 50% of spontaneous miscarriages?
Chromosomal abnormality
What is mosaicism?
Presence of 2 or more cells lines with different genetic makeup in an individual
Mosaicism - how can some cells have trisomy and others not? What about an Down syndrome embryo?
Non-disjuction during an early division after fertilization. A DS embryo in which some cells revert back and lose the extra chromosome
