Principles of Clinical Cytogenetics Flashcards
Define “Clinical Cytogenetics”
The practice of medical genetics y studying the structure and number of chromosomes to identify their abnormalities / disorders.
Define “Aneuploidy”
One or more extra or missing chromosomes. ex: 45 monosomy or 47 trisomy.
Define “Polyploidy”
having more than two complete sets of chromosomes.
How many chromosomes does someone who has trisomy have?, how many chromosomes does someone with triploidy have?
Trisomy: 47 chromosomes
Triploidy 69
What is a Robertsonian translocation?
A translocation between two acrocentric chromosomes by fusing at or near the centromere with the loss of the short p arms.
1) What type of cells are harvested for routine karyotyping analysis?
2) What is colcemid used for?
1) T lymphocytes
2) It prevents spindle formation, thus arresting cells at metaphase
1) What is in a Giemsa stain?
2) Which parts of chromosomes are stained more darkly in G-banding?
1) Methylene blue, eosin, azure B
2) AT- rich regions are darker than GC- rich regions
1) What are the three classifications of chromosomes based off centromere location?
2) Give an example of each.
1) metacentric, submetacentric, acrocentric
2) Chr 1, 2, 3 Chr 4, 5 Chr 13, 14, 15, 21, 22
1) What is in a Q- banding stain?
2) Why is Q- banding performed?
1) Quinacrine mustard
2) used to detect heteromorphism between homologous pairs
1) What is in a R- banding stain?
2) Why is R-banding performed?
1) Giesma, and quinacrine. It differs by the specimens being heated before staining which causes the dark and light bands to be reverse?
2) To study the distal ends of chromosomes
1) What is used in a C-banding stain?
2) Why is C-banding performed?
1) A xylene substitute
2) it makes it easier to study centromeric regions that still have constitutive heterochromatic
1) What is Spectral Karyotyping (SKY)?
2) What can SKY identify?
1) 24 probes, one for each chromosome (X and Y are different) are combined and used for Fluorescent In Situ Hybridization (FISH) of metaphase chromosomes. where each probe will have its own color.
2) abnormal chromosomes consisting of pieces of different, translocated chromosomes.
How is a complementary DNA (cDNA) library formed?
mRNA is reverse transcribed into coding DNA which is inserted into host vector cells. If all the mRNA of the organism is inserted, then that collection of vectors constitutes the transcriptome of the organism.
1) What is Comparative Genome Hybridization (CGH) used to determine?
2) What is a limitation of CGH?
1) Used to determine the copy number/ dosage differences between two different DNA samples.
2) deletions or duplications smaller than 5 - 10 Mb can not be detected.
In Whole-Genome Sequencing what does the alignment of sequence reads from a patient’s genome to the reference sequence of 2 chromosomes reveal?
a chromosomal translocation event occurred so that one sequence is adjacent now found on two chromosomes
