The price of a personal genetic profile is about to get a lot lower.

23andMe, one of the leaders in the new field of consumer genetic information, is expected to announce on Tuesday that it is cutting the price of its service deeply, to $399, down from $999. Linda Avey, a co-founder of the company, said the move reflected improvements and lower costs for devices, made by Illumina of San Diego, that are used to scan a person’s genome.