This story is a pure yuri.
The setting can be seen as "stupid", "unrealistic", "yaoi" or a "commentary about our own world", but I'd say it's mainly inspired by Takarazuka Theater, as hinted in the note of this page.
Takarazuka is a all-female revue, where the actresses are either musumeyaku (female role) or otokoyaku (male role).
When you enter in Takarazuka, you enter in a fantasy world with only "women". It's the same with Love DNA.
The otokoyaku (and thus the Adam in the manga) isn't male, but she is the incarnation of the ideal shōjo, who manage to be both the "ideal man" and the "ideal woman", the prince and the princess.
A shōjo isn't simply a "little woman", but she is more or less considered as a third gender by the japanese gender studies, distinct from male or female. There is a ton of things to say about "what is a shōjo exactly?", but I like this definition: "the shōjo is a female yet sexless being, with homosexual experience and heterosexual inexperience". That's the foundation of the yuri, especially the Class S thing of the prewar Japan, homosexuality between shōjo, and not women.
Takarazuka is one pillar of the shōjo (and thus yuri) culture/identity (the other pillar is Nobuko Yoshiya, the author of the first yuri (Class S) stories). You can find its influence everywhere in shōjo, yuri and even yaoi manga. From Princess Knight to Rose of Versailles, Utena, Sailor Moon, Oniisama e…, Kaze to Ki no Uta or Ouran High School Host Club.
Love DNA is simply a continuation of this tradition. And it's one of the more "genderfuck" yuri out there, far behind Simoun, but still. At first I was lost by Simoun too; for me the heroines in this story weren't women, or even girls, they were children, sexless, and thus speaking of "yuri" for Simoun was absurd in my eyes. But now, after reading studies about shōjo/yuri, I understand that Simoun is the best example of what yuri is. Love DNA takes another route than Simoun, but is similar in many ways.
If you're interested by the otokoyaku, the shōjo et cætera, you can easily find information about it in virtually all scientific studies of the shōjo/yuri manga, and a little in yaoi manga (where the bishōnen archetype is inspired by the otokoyaku too), many of them are freely readable on the internet.
But this one is a good start, I think : https://webspace.yale.edu/anth254/restricted/AE_1992_19-3_Robertson.pdf
This. This. This. This. This.
