- Created by: MazzaW
- Created on: 29-11-19 14:12
Banding and pairing alike chromosomes. Done in lithium heparin sample (14 days turnaround time)
Can show: aneuploidies, balanced/unbalanced translocations, large deletions/duplications
- Down's (trisomy 21/unbalanced Robertsonian translocation in 2%): 47 **/XY +21
- Edward's (trisomy 18): 47 **/XY +18
- Patau's (trisomy 13): 47 **/XY +13
- Klinefelter's: 47 **Y
- Turner's: 45 X
Fluorescent in situ hybridisation
Attaches fluorescent tracers to specific DNA sequences
Can detect: aneuploidies, specific deletions and duplications, specific mutations
Can detect abnormal numbers of genes (should have 2)
Useful for: aneuploidies, unbalanced translocations, deletions/duplications
Quantitative fluorescent PCR
Rapid screen for common trisomies and sex chromosomes in neonates.
Done in 1-2mL EDTA sample with 48hr turnaround time. If abnormal, should be followed up with karyotyping.
Should have 2 peaks (for 2 different alleles) - in trisomies, have 3 peaks or increased size of 1 peak.
Whole exome sequencing
If pt likely to have a single gene defect but normal CMA and no abnormality seen on sequencing likely genes, can do whole exome sequencing.
Includes all exons, ultraconserved regions, regulatory regions, ncRNAs, enhancers, splice donor + acceptor regions.
Will show ALL abnormalities, including normal variants (normally 30,000 per exome):
- filter out common variants and variants unlikely to have an effect
- select only the variants in relevant disease genes
- look at parental genotypes/phenotypes and select variants with relevant inheritance (e.g. de novo, recessive)
- try and work out which gene is the cause- clinical input required