A set of mutations that REGULATE / REGULATES genes

Question

I am trying to wrap my head around the usage of 'that' in these two sentences. While I got the answers correctly when I tried to understand the meaning of the sentence, I am wondering if there is any grammar rule that I am missing out here.

1. A study found that many autistic children share a set of mutations that regulate/regulates genes known to influence communication among brain cells.

2. The department is taking a stand against an approach that stand/stands to make an indebted citizenry more dependent on federal.

In sentence 1, it seems that that refers to 'a set' In sentence 2, it seems that that refers to 'approach'. Why does it not refer to 'a stand'?

Is there any rule that I can follow for 'that' in this context? For example, I read somewhere that 'that' must modify the noun immediately preceding it, but in example 1, that rule does not work. Also, somewhere else, I read that 'that' does not modify prepositional phrase. This works for 1 (of mutations is ignored), however for 2 this fails since (against an approach) is a prepositional phrase.

Answer 1

"I read somewhere that 'that' must modify the noun immediately preceding it"

This generalisation is a good one - almost. A relative clause usually occurs directly after the phrase it modifies. When the antecedent is headed by a noun this means that the relative clause occurs directly after the Noun Phrase that it is modifying. The word phrase there is crucial.

Noun phrases often contain smaller noun phrases inside them. So for example in the phrase the man of the moment, there is a smaller noun phrase, the moment. So whether the verb REGULATE should agree with the noun phrase a set of mutations or the noun phrase mutations depends on which noun phrase is the understood Subject of the verb. (In this case it doesn't really matter very much)

In the second example, the antecedent for the relative clause could be either of the following noun phrases:

• a stand against an approach
• an approach

It isn't possible to tell which is intended without further context. However, in this case the two sentences will mean radically different things depending on what the antecedent noun phrase is.

Answer 2

The (nested) noun phrases immediately preceding that in #1 are:

• mutations; and
• a set of mutations. (cf BillJ's comment)

There's no simple rule that says whether it refers to the whole phrase or the last of the nested noun phrases. It must be determined from context (cf Barmar).

For example, using nested brackets identify the candidate noun phrases, "a (school of (children of (farmers))) that" could be followed by "conducts exams", "sit exams" or "grow crops".

That refers to the noun phrase immediately preceding it. In #1, since there are two candidates, it is possible for that to refer to mutations (Barmar), but it's also possible for that to refer to a set of mutations.

Answer 3

Does the set regulate genes as a whole, or do the mutations individually regulate the genes? The verb should agree with whichever noun regulates the genes.

In this case, it seems quite possible that both nouns could be said to regulate the genes, in which case both answers would be correct.