How does Mikoto know about the Sisters before the Sister's Arc?


Misaka Mikoto seems to know about the sisters before the Sister's-arc, as she
says both in the prologue of the first LN and the Railgun-manga:

> Have you heard how my DNA map was supposedly analyzed and military Sisters
> were created based on it?

How did Mikoto know about the Sisters back then? She found out during the
Sisters Arc (which happened later) that the Sisters exist and the rumor just
spread then, too (at least it seems to me). How could she tell Touma about
them?




After Mikoto meets Nunotaba Shinobu, she [starts
investigating](http://toarumajutsunoindex.wikia.com/wiki/Sisters_Arc#The_First_Production_Plan)
her and finds her connection with the 7th Medical Research Center, who were
researching her DNA map to create an army of level 5 clones.

This is covered in the _Railgun_ manga and _Railgun S_ anime.

Initially she thought the Sisters project was abandoned because the clones
would only be Level 3 (thus not realizing the plan for an army of Level 5
clones), but it's not until later that she realizes the Sisters were utilized
for the Level 6 Shift project.




After Mikoto meets Nunotaba Shinobu, she [starts
investigating](http://toarumajutsunoindex.wikia.com/wiki/Sisters_Arc#The_First_Production_Plan)
her and finds her connection with the 7th Medical Research Center, who were
researching her DNA map to create an army of level 5 clones.

This is covered in the _Railgun_ manga and _Railgun S_ anime.

Initially she thought the Sisters project was abandoned because the clones
would only be Level 3 (thus not realizing the plan for an army of Level 5
clones), but it's not until later that she realizes the Sisters were utilized
for the Level 6 Shift project.

