Hello!

I have two questions concerning defining/non-defining relative clauses.
Please look at the example sentences below :

a. Mr.Brown has a daughter who became a doctor.
b. Mr.Brown has a daughter, who became a doctor.

Q1. What's the difference in meaning?
Q2. When you hear these sentences separately, do you recognize the difference in meaning? If so, how? Do you put a pause between the clauses? (It's quite hard for me to decide which(defining/non-defining) when they are spoken.)


Thank you in advance!