Which of these nouns should the verb agree with?

Question

While I understand the basic grammar rules of the verb used in restrictive clauses, I came across many sentences like the example below, supposedly written by a native speaker (?).

Disease A is due to mutations in the X gene that result in ...

I thought the verb "result" should be "results", as the noun immediately in front of the relative pronoun "that" is gene, which is singular. Understandably, the clause is actually used to describe the "mutations", so it also seems correct to use "result", not "results".

Which verb is correct?

Answer 1

The subject is "mutations", so a plural verb "result" is expected, and normal.

Having said that, the closer noun often does exert some influence, and you will hear the singular "results", particularly in informal contexts. Some people castigate this use as "wrong".

Answer 2

To expand on Colin Fine's answer a bit, "that" isn't always a noun. "That" is often a conjunction, like in the provided fragment. "Disease A is due to mutations in the X gene" is a complete sentence on its own. "That" is joining it with another sentence that is expanding on "mutations", creating a larger sentence.

"Disease A is due to mutations in the X gene. Those result in ..." and "Disease A is due to mutations in the X gene; those result in ..." are alternatives using "those" instead of "that". Notice the two parts are separate sentences in both, instead of one sentence with a conjunction.