Our golden retriever has had 5 puppies and we have kept one of them. Mother plays very hard with daughter often pulling her by the tail and play biting her ear. They jsut seem quite aggressive together though they don't really hurt each other. Should we keep them separate until puppy (9 weeks) is old enough to stand up to it or should we put them together more so they go through it. We have tried both options for the last 6 days but it doesn't seem to get any better. Mum is 4. Thanks

Don't keep them separate! This is normal canine behaviour. Just monitor their play - mum is teaching her puppy essential (canine) survival techniques.

It seems to be Mum who is almost more aggressive and chases the puppy. Is this also normal?

My mother and daughter used to appear to 'play' very agressively, mother did appear to be too rough with pup but there was never any serious intent. It is I'm sure a learning thing for pup.
I never interferred with this learning curve, I just watched and made sure that all was good and pup was safe.

My pup is now 9 months and they still have massive amounts of team tag rough type play only now pup is faster and can leave her mum standing, when pup gets too boisterous mum nips her to shut her up, normal doggy stuff I reckon.

I would agree that it's perfectly normal.  I would only ever intervene if blood was spilled.  I've had mother and daughter play fights that have sounded as if one was killing the other.  But never any genuine hurt.

I've always thought that it was how lessons were taught.

Although often what you're describing is normal and, as others have said, part of the process of raising a pup...

... it is not the case that necessarily your situation is.  I have known of a mother dog 'turning' on a pup which was kept behind and bullying it, to the point that the pup became very miserable and depressed.  In the end, pup was rehomed. 

Just as there are some mothers who abandon their litters or - even worse(!) - eat them, so there are some mothers who are fine with the baby-puppy stage but then decide they'd rather prefer life without pup around. 

I think it is impossible to tell, from descriptions on an online forum, what the situation is and I'd be hesitant to reassure you that all is well and it's all perfectly normal with so little to go on. 

It does sound like you are concerned about the pup, from your account of things, and often our gut instincts are right.  I'd suggest perhaps videoing what is happening and showing it to some experienced doggy folk and also breeders, to see if they agree that it is 'normal' or not. 

To be honest, I would err on the side of caution if you're at all unsure.  This means supervising their interactions, having time out during the day with part of the day spent separately in separate rooms or with one crated and one not - and perhaps having mum on a house line when they are playing together, so pup feels she can get away if she wants to and isn't pursued and pursued...  Do be aware, too, that you should be spending one-to-one time with the pup training and playing, so that pup doesn't get all play with mum and get overly attached to mum and other dogs, and not at all to you.