andrew e - I can sing in tune alone but in a choir am guessing from the music. One of my choir directors tells me relative pitch can be learned but perfect pitch (which I would say she has) seems to be more genetic?

To JHW

You need to learn your part as if it was the "tune".
To you that's how the song goes.

I don't have perfect pitch, and have never met anyone who has!
I use a tuning fork for opening notes.

It's all relative, but also I think a short term memory of a pitch,can be developed with exercises, particularly for A Cappella singing.
For instance singing a semitone scale, and imagining/hearing in your head the first note whilst doing this.
Most community choir singers don't get this far.