Nope. A law. A theory has a unifying, underlying principle to it, such as evolution being caused by natural selection. Whereas before 1952, people knew there were dominant and recessive genes, and they even knew which chromosome the genes were located on, but they had no deeper knowledge of what the genes were physically, or what caused a gene to be dominant or recessive.
Your definition of "underlying principle" is in that case subjective.
Mendel would argue that "units of inheritance" which are dominant or recessive, is an underlying principle. So would I.
The extra detail you get from associating genes with DNA sequences is just detail.
How much detail do you need before it becomes, in your view, "fundamental"?
(1) Genes are identified with DNA sequences
(2) Genes are identified with possibly multiple copies of DNA sequences.
(2) As above but the DNA sequences are expressed or not according to stuff generated from other DNA sequences, thus switching genes on and off?
(3) as above but all of the details that determine gene expression.
Without all of the details, you have an inexact model. You choose to set and arbitrary dividing line between what is "fundamental" and what not.
Another example would be electricity.
Maxwell's laws are more fundamental than Kirchoff's Laws
Yet both are highly predictive, and they predict (quantitatively) new experimental results: so they are more than just "this happened - so it will happen again". Even constancy can be an important predictive theory:
"mass is conserved in any chemical reaction" - is not obvious, and predicts new experiments and important,
Jed: I'd recommend to you, when thinking about things, to entertain the possibility that what seems certain to you may be the opposite of certain to other people. Not because they are stupid, or have an agenda, or biased. Just because they think about things more in shades of grey (if that is an expression that can now be used without inappropriate associations!).
In this case you think you have an "obvious" distinction between laws and theories that are fundamental. I disagree. If I had to distinguish I'd say that a scientific theory:
(1) Must generalise from past experiments to make new future predictions (not just - mass is conserved in the reaction 2H2 + O2 -> 2H2O - bit "therefore mass is conserved in all reactions"
(2) Those predictions (of new experiments) must prove correct and informative (in a Bayesian sense, rather than saying nothing that was not already known).
the above definition is not quite complete - if anyone challenges it I will try to elaborate.