Essential features of a claim are those necessary for achieving a technical effect underlying the solution of the technical problem with which the application is concerned (the problem usually being derived from the description). The independent claim(s) must therefore contain all features explicitly described in the description as being necessary to carry out the invention. Any features which, even if consistently mentioned in the context of the invention throughout the application, do not actually contribute to the solution of the problem are not essential features.
As a general rule, the technical effect or result produced by the feature will provide the key to answering the question of whether or not the feature contributes to solving the problem (see also G‑VII, 5.2).
If a claim is to a process for producing the product of the invention, then the process as claimed must be one which, when carried out in a manner which would seem reasonable to a person skilled in the art, necessarily has as its end result that particular product; otherwise there is an internal inconsistency and therefore lack of clarity in the claim.
In particular, where patentability depends on a technical effect, the claims must be so drafted as to include all the technical features of the invention which are essential for the technical effect (see T 32/82).
Claims towards plants or animals which are not exclusively produced by an essentially biological process comprising a functionally defined phenotypic trait and which are worded as product-by-process claims (i.e. obtainable by crossing a plant with a plant grown from deposited seed having accession number XXX and selecting for a progeny plant comprising the phenotypic trait) must fulfil the clarity requirement of Art. 84, as must any other type of claim. In particular, the claimed subject-matter must be defined so that the public is left in no doubt about what the subject-matter for which protection is sought actually is. If the process through which the claimed plant or animal is defined does not impart identifiable and unambiguous technical features to the plant or animal, e.g. the genetic information present in the genome, the claim directed to a plant or animal lacks clarity.