Genetic Testing

Question 1

What can a conventional karyotype diagnose?

Answer 1

Detects aneuploidy, large chromosome imbalances, balanced and unbalanced translocations
Eg: Trisomys, CML

Question 2

What can FISH diagnose?

Answer 2

Detects the presence or absence of specific DNA sequences on chromosomes, Must be looking for a specific target

Question 3

What is a chromosomal microarray? What can it diagnose?

AKA CGH microarray

Answer 3

Compares DNA from 2 sources - a test and a control sample –> looks at gene gains and losses
Detects large and small additions and duplications as well as small losses and monosomies HOWEVER introduces the concept of variations of unknown significance

Question 4

What can a SNP array diagnose?

Answer 4

SNP only = genotype abnormalities without gain or loss of genetic material - chimerism/mosaicism, uniparental disomy
CGH + SNP microarray = copy number abnormalities - microdeletions and microduplications

Question 5

What can a Sanger sequencing diagnose?

Answer 5

Used to determine the exact sequence of bases = diagnosis of marfans, neurofibromatosis, CF

Question 6

How do you diagnose a triplet repeat disorder?

Answer 6

PCR CTG sizing and Southern Blot

Question 7

How do you diagnose an imprinting disorder?

Answer 7

Methylation sensitive MLPA

Multiplex ligaiton-dependent probe ampification