And they often use karyotyping, a process of spreading out and counting a cell’s chromosomes, to confirm that the reprogramming process didn’t introduce major genetic abnormalities, a rare but possible outcome.

Karyotyping remains a useful technique for pinpointing large abnormalities, but the level of resolution is limited to about 5m base pairs.

Traditionally, geneticists like Firth used a process called karyotyping, which involves pairing up and ordering all the chromosomes to see if any are missing, duplicated or contain subtler structural changes.

Human ES cells underwent routine mycoplasma screening and karyotyping.

Graduate students and postdoctoral associates will then lead small groups of students in activities including DNA extraction and karyotyping for chromosomal differences.