Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
The fragments are classified in four spectral groups N1–N4 (the sample numbers of each group population are given in Supplementary Table 1).
