Question

1. Microarrays are now used as prenatal diagnostic tools to identify aneuploid fetuses in humans. Prospective parents also get to know the sex of their child if microarray profiling is performed. Give some thought to the potential for microarray-based verification of karyotypes in including and beyond the human species. Then indicate whether the sex of a fetus could be determined in the following species by this method. If so, for each case, should the microarray be hybridized to genomic DNA or cDNA? If either DNA or cDNA would be inappropriate, explain why.

1. Chickens (sex is determined by ZW chromosomes)

2. Snakes (sex is determined by alleles of a single gene)

3. Agama lizards (sex is determined by the temperature at which eggs hatch)

4. Twelve year old human suspected to be X0 (Turner’s syndrome)

Answer 1

microarray based comparative genomic hybridisation is a type of cytogenetic test that uses DNA and provides much greater detail and higher resolution of parts of chromosome that are extra or missing. The regions studied are often linked to birth defects, intellectual disability or any other medical or learning problems. Karyotyping is traditional cytogenetic testing that detects chromosome deletions and duplications.

clinical utilities of microarray profiling

1. postnatal diagnosis of developmental delay or mental retardation or congenital anomalies
2. prenatal diagnosis - microarray karyotyping helps in unmasking of translocaton- associated imbalances
3. infertility and recurrent abortions
4. Mosaicism detection
5. Aneuploidy detection
6. constitutional genetic diagnosis
7. genomewide genotyping
8. analysis of cell free foetal DNA in amniotic fluid
9. In human constitutional cytogenetics.

Chromosomal microarray is a first tier clinical diagnostic test for individuals with developmental disabilities or congenital anomalies. This method can be used to determine the sex of chickens and also to determine the presence of XO in a 12 year old child.

Microarray should be hybridised to genomic cDNA