Flashcards in 2F- Clinical Cytogenetics Deck (81)
What is a karyotype?
refers to the number and type of chromosomes present in an individual
What phase of mitosis are chromosomes are maximally condensed and easiest to see?
What is the term when the p and q arms are of equal length?
What is the term when the p arm is smaller than the q arm?
What is the term when the p arm contains no genetic information and just contains a stalk and satellite?
What is a telomere?
The tip of each chromosome that is repetitive and protects the chromosome from degradation.
What is a satellite?
seen with an acrocentric chromosome, the short arm (p arm) may just be a little nubbin, which is called a satellite which is connected to the chromosome by a stalk.
What is banding?
Chromosome banding helps greatly in the detection of deletions, duplications, and other structural abnormalities, and it facilitates the correct identification of individual chromosomes
What is G-banding?
Most common staining technique used. Giemsa stain is applied after the chromosomal proteins are partially digested by trypsin
What is R-banding?
best for staining the Distal Ends of the chromosomes, it requires heat treatment and reverses the usual white and black pattern that is seen in G-bands and Q-bands
What is Q-banding?
early method that requires fluorescent microscope, not used much now
What is C-banding?
stains the constitutive heterochromatin, which usually lies near the centromere
What is constitutive heterochromatin?
heterochromatin that is found near the centromere and is stained with C-banding.
What is high resolution banding?
chromosome staining during prophase or early metaphase (prometaphase), before max condensation and when they are more extended. This increases the number of bands observable to about 300 to 450 to as many as 800.
What is cool about high resolution banding?
This allows the detection of less obvious abnormalities usually not seen with conventional banding.
What is the goal of FISH?
You use a piece of DNA what will only bind to a certain known area of the chromosome, the DNA you are using will fluoresce indicating that it did bind to the chromosome where it was supposed to.
What is FISH used for?
to detect deletions (normal pt's will have fluorescent probe attach, if deleted then it doesnt attach)
What if you see more glowing pieces than you should?
There is a duplication of the gene targeted by the probe (or it could be a trisomy)
What is spectral karyotyping?
you use varying combinations of five different fluorescent probes so that each chromosome is uniquely colored, which is useful for identifying small chromosome rearrangements
What is comparative genomic hybridization used for?
detect losses or duplications of whole chromosomes or specific chromosome regions
What is the comparative genomic hybridization procedure?
label normal DNA one color and label cancer cell DNA another color, and put them in a metaphase preparation and see which hybridizes, you then measure the color to detect loss or gain of material
In CGH, if there is a deletion in the mutant chromosome, what color will show?
The color used to label the normal DNA will show.
In CGH, if there is a duplication in the mutant chromosome, what color will show?
the color used to label the abnormal DNA will show
Why is CGH better than FISH?
highly automated, requiring less time from laboratory personnel. There is no need for dividing cells, and a minute amount of DNA is sufficient for analysis of the entire genome
Why is CGH worse than FISH?
cannot detect balanced rearrangements (reciprocal translocations or inversions.)
What is euploidy?
a cell that contains a multiple of 23 chromosomes
What is polyploidy?
cell that contains a multiple of 23 chromosomes greater than 46
What is triploidy?
nucleus with 69 chromosomes
What is the cause of triploidy?
usually caused by egg being fertilized by two sperm (dispermy)