Lec 10. Medical Cytogenetics Flashcards
What is the difference between constitutional and acquired cytogenetic? abnormality
Constitutional can happen before conception and a little later after fertilization. Acquired happens during teens or adulthood.
What are some main reasons for cytogenetic analysis?
For prenatal analysis: abnormal NIPS, old mother, fxh of chromosome abnormality, mom anxiety, abnormal ultrasound. For Postnatal analysis: multiple miscarriages. For cancer: tumors
What are the steps of diagnostic testing workflow?
- pt comes and sees doc that determines what test to use. 2. Send pt to lab, draw blood etc. 3. Test sample. 4. Geneticists see results and then send to doc. 5. Pt gets results.
What is medical cytogenetics?
Part of clinical medicine that studies relationship between chromosomal alterations and genetic disease in humans
When was the cytogenetics inception?
Late 1950’s
What did T.Painter do?
Section of human testis with spermatogonial mitosis, leading to drawing of human spermatogonial metaphase
What did T.S.Hsu do?
Tissue culture accidentally treated with a hypotonic solution, leading to chromosome grouping based on size and placement of centromere.
What are the 3 major cytogenetic methods used in clinical genetics diagnostic labs?
G-banding chromosome analysis, FISH, microarray analysis
What are the advantages of G-banding chromosome analysis?
1.Fast. 2. Detection of numerical abnormalities; structural chromosomal rearrangements; large depletions/duplication
What are the disadvantages of G-banding chromosome analysis?
Requires lots of training, minimal size of detected imbalance 5-10 mb. Low-level or tissue specific mosaisism may be missed, EPIGENETIC changes not detected. Cancer:no dividing cells = no chromosome to analyze.
What are the advantages of FISH?
Doesn’t require dividing cells, quick screening of large number of cells, rapid results, confirmatory test to G-banding analysis, May detect mosaicisim, improved detecting of chromosomal alteration in neoplasia, can detect small deletions/duplications up to 50 kb.
What are the disadvantages of G-banding chromosome analysis?
Needs physician to suspect diagnosis, costly, EPIGENETIC changes not detected
What are the advantages of DNA Microarray?
Up to 5kb size for detection of imbalances, small amount of input DNA, comprehensive evaluations of deletions/duplications/amplifications in analysis, Mapping DNA del/dup to a specific chromosome location. Ability to determine gene content within the region of del/dup. Prior knowledge of nature of gene aberration not necessary for FISH, no requirement for tissue culture or metapahse preparation from the test specimen.
What are the disadvantages of DNA Microarray?
Balanced chromosomal rearrangements are not detected* challange in interretation of DNA copy number variations.
21 y/o F pt presents to the ED with developmental delay, sleep disturbance, self-injury behavior, speech delays, deep hoarse voice, you suspects smith Magenis syndrome. Which of the 3 tests do you order?
G-banding chromosome analysis