Answer: invivo
A person has a genetic condition that affects his ability to produce melatonin, which is a hormone that is produced in the brain and tells the body it’s time to sleep. To correctly diagnose this disease, the doctor must collect cell samples invivo to analyze his DNA.
Step-by-step explanation:
Invivo refers to the within the living organism. Since DNA is located inside the nucleus of brain cells, and it regulate gene expression; then the doctor must analyze the genetic information contained in the DNA of brain cells of the person having trouble with secreting melatonin ( the sleep/wake hormone), if any alteration has occurred.
Thus, based on the location of DNA, the doctor must collect cell samples invivo for analysis