No objection on account of lack of unity a priori is justified in respect of a dependent claim and the claim on which it depends, on the ground that the general concept they have in common is the subject-matter of the independent claim, which is also contained in the dependent claim. For example, suppose claim 1 claims a turbine rotor blade shaped in a specified manner, while claim 2 is for a "turbine rotor blade as claimed in claim 1 and produced from alloy Z". The common general concept linking the dependent with the independent claim is "turbine rotor blade shaped in a specified manner".
If, however, the independent claim appears not to be patentable, then the question whether there is still an inventive link between all the claims dependent on that claim needs to be carefully considered (see F-V, 7, non-unity "a posteriori"). It may be that the "special technical features" of one claim dependent on this non-patentable independent claim are not present in the same or corresponding form in another claim dependent on that claim (see also C-III, 4.1).
Any claim which refers to an independent claim but does not include all of its features is an independent claim (Rule 43(4)). Examples are a claim referring to another claim of a different category, or a claim specifying an alternative feature which is intended to replace a corresponding feature in the independent claim referred to (for example, an apparatus according to claim 1, wherein component C is replaced by component D).