Diagnostic Technologies 4 Flashcards
What probes used to be used for FISH, what probes are used now?
Before 1980s - radioactive compounds seen with xray
Now: fluorescent dyes
Describe the nature of the fragment you would want to use as a probe?
DNA unique to region - locus specific
What phases of the cell cycle can FISH be used on?
metaphase and interphase
What are the three types of FISH?
- repeat sequences
- single copy DNA
- chromosome painting
Which type of FISH uses a cocktail of many unique DNA fragments along the length of a chromosome as probes?
chromosome painting
Which type of FISH uses isolated DNA from disease causing gene?
single copy DNA
Which type of FISH is a subtelomere FISH an example of?
single copy DNA
Which type of FISH uses centromeres and telomeres as probes?
repeat sequences
What can repeat sequence FISH be used for?
identify a specific chromosome
identify monosomy and trisomy
What is chromosome painting especially useful for?
translocations
What are three caveats of using FISH?
- probes dont usually cover entire deletion
- deletion may be present, but cant be detected
- clinical diagnosis always trumps FISH
What occurs at the chromosomal level in a VCFS patient?
3 MB deletion on chromosome 22
What are contiguous gene syndromes?
regions in genome with clusters of closely associated genes
What chromosome is the deletion for william’s syndrome on? what genes are known to be involved?
chromosome 7
elastin gene, autistic like behavioral control gene
What are some symptoms of VCFS?
- learning diabilities
- short stature
- cleft lip and facial anomalies
- hypotonia
- cardiac anomalies
What process results in the deletion that causes VCFS?
unequal crossing over - wrong repeats pair up leading to missalignment
Why are parents with children with VCFS, that have same deletion, clinically normal?
it all depends on the combination of alleles and how other gene products are able to compensate
In comparative genomic hybridization what do the colors green and red mean?
green - excess of reference DNA - deletion
Red - excess of test DNA - duplication
What is a disadvantage of a gene array?
it doesnt detect balanced rearrangements - total amount of DNA is conserved
What are the three steps to forming an expression array?
- DNA fragments representative of genome- slide
- RNA is extracted from tissue of interest
- cDNA is made with labeled fluorochrome
see which genes are expressed in each tissue
What are microarrays used for?
to see which genes are up-regulated in tumors from various tissues
What do the peaks and valleys in chromosome microarrays represent?
peaks - duplications
valleys - loss
What should be the first study done in a case of unexplained developmental disorders, autism, multiple congenital abnormalities?
microarray
What are the people called that sorta data for the lazy geneticists?
bioinformaticians
How has next generation sequencing become simplified and maximized its gains?
targeted sequencing
does insurance cover next generation sequencing?
no not right now
