compound sentences - A comma before "and consequently?" After "and?" After "consequently?"

Consider the following example:

Apples are healthy and consequently serve as a powerful tool in preventing diseases.

Where should I place a comma (or commas) in the above sentence?

If I change the above example to:

Apples are healthy and consequently they serve as a powerful tool in preventing diseases.

Where should I place a comma (or commas) in the above sentence?

Any help would be greatly appreciated.

Answer

This isn't a comprehensive answer about the overall use of commas, but it addresses your question directly.

I was taught a simple way to remember if a comma should be used in instances like yours.

Use a comma if you have a full sentence after "and".

For example, sentence one doesn't need a comma. "Apples are healthy." is a complete sentence, but "Consequently serve as a powerful tool in preventing diseases." isn't a complete sentence because it lacks a subject.

Sentence two does need a comma because "Apples are healthy." and "Consequently they serve as a powerful tool in preventing diseases." are both complete sentences.

Sentence two should be written "Apples are healthy, and consequently they serve as a powerful tool in preventing diseases."