Genetic testing Flashcards
Cytogenetics
Physical structure and composition of chromosomes
Eg. karyotype
Molecular cytogenetics
Combination of molecular biology and cytogenetics
Eg. FISH, molecular karyotype
Conventional karyotype
Visually analysis whole chromosomes
Detects aneuploidy, large chromosomal imbalances, balanced and unbalanced translocations
10-12 days
FISH
Fluorescence In Situ Hybridisation
Detects presence/absence of specific DNA sequences on chromosomes
Fluorescent-labelled DNA probes for specific target
CGH
Comparative Genome Hybridisation
Compare DNA (genome) from 2 sources: test and control
Looks at gains/losses of DNA content i.e. difference in amount of genetic material
Chromosomal microarray
Uses array based CGH method or SNP arrays
Detects unbalanced chromosome changes
Microarray detection
CGH & SNP: copy number abnormality
- microdeletions
- microduplications
- trisomy
- single gene diagnoses (some)
- CGH mosaicism approx 15%
SNP only - copy number neutral with genotype abnormalities
- chimerism
- uniparental disomy
- LCSH (long continuous stretches of homozygosity)
- mosaicism approx 7%
Sanger sequencing
Determines exact sequence of bases
PCR
Polymerase chain reaction
Used for amplification of sequence of interest
Linkage analysis
Indirect test
Based on linkage = genes that are close together are inherited together (chromosome exchange at meiosis)
MLPA
Multiplex Ligation-dependent Probe Amplification
Modified PCR amplification
Detects deletions and duplications of any gene
Cannot detect sequence changes or large copy number changes
Methylation sensitive MLPA
Can detect methylation ie. parent of origin of sequence of interest
Used for imprinting disorders (Eg. Prader Willi, Angelman, Beckwith Wiedermann)
