Cytogenetics Flashcards
1
Q
numerical abnormalities
A
- change number of chromosomes
2
Q
structural abnormalities
A
- change structure of chromosomes
3
Q
robertsonian translocation
A
- fuse two small chromosomes into a very large chromosome
4
Q
historically
A
- chromosome rearrangements have involved large regions of genome because they have been detected by karyotyping
5
Q
limits of karyotyping
A
- requires viable cells
- low resolution limited to 3-5 MB or greater
6
Q
karyotyping used for
A
- permits evaluation of entire genome
- used to detect gains and losses of entire chromosomes and fairly large chromosomal regions
7
Q
why do chromosome abnormalities result in disease
A
- cause an increase and/or decrease in gene products
- alter the gene product itself by producing a fusion protein with altered function
8
Q
what phenotypes are typically associated with chromosome abnormalities
A
- cancer
- abnormal growth and development in children or pregnancies
- early death
- clinically normal individuals with a personal or a family history of clinical abnormal offspring, miscarriages, or infertility
9
Q
FISH
A
- high resolution - usually 100 KB
- requires clinically directed search
- very specific search
- interphase FISH can be performed on nonviable cells
10
Q
FISH technique
A
- chromosome prep and denaturation
- labelled probe and denaturation
- in situ hybridization
- detection
11
Q
micro deletion and micro duplicating syndromes characterized by
A
- by small, recurring interstitial deletions or duplications
- each associated with a well described phenotype
12
Q
DiGeorge syndrome
A
- facial features - prominent nose w/ squared nasal root, small yes, small ears with abnormal folding
- abnormal palate
- heart abnormalities
- learning disabilities
- hypocalcemia
- immune deficiency
- psychiatric disorders
13
Q
DiGeorge syndrome FISH
A
- green control maps just fine
- red probe which normally maps to DiGeorge critical region does not hybridize
- that region is deleted on chromosome 22
14
Q
microarray tech allows us to
A
- survey entire genome for gains and losses
- very high resolution
- can use nonviable cells
- allow us to identify consanguinity and probably uniparental disomy
15
Q
how affymextrix cytoscan array works
A
- patient DNA is labelled with fluorochrome probe and allowed to hybridize to a chip containing arrayed DNA of interest
- intensity of hybridization signal at each locus is compared to the in silico data obtained from 270 normal controls to assess copy number
- data for each locus plotted as a log 2 ratio of 0
