rottweiler 6 weeks old!

Question
QUESTION: i bought a 6 week old female rottweiler which is my first dog.it has been only 2 days since i got her.my problem is that she is a bit aggressive sometimes.when we do things she doesnt want us to do she growls and snaps.like when she is chasing a cat i went and lifted her up.she growled and tried to bite.when making her lie on the back and scratching her belly she tries to snap and roll back.i dunno whether it is natural behaviour that she growls and tries to bite as this is my first puppy.only sometimes she does this rest of the time she is peacefull with us.she gets mouthy but never growls.i have heard that growling is a symptom of "alpha dog".we give food only after we eat,am the first to come out of the door and go inside,sheis never allowed to sleep with us but still i dont understand y she is alpha!when shud i start training her?

ANSWER: Karthik,
of course I am not there to actually see this, but at 6 weeks I would say she is working on instinct.  Keep putting her on her back and dont let her up until she submits.  Make sure you stay the boss.   So far you are doing everything correctly.  Start training her now, but not with correction, train her with treats (sit, stay, down).  Make sure you take her food away from her and give her a treat to replace it, and then return the food.   IF, when she is older, (3-6 months) she bites hard and means it, that will be the time to come down hard on her.  For now she does not get her way, but no corporal punishment, she is too young and you dont want to change that instinct to fear biting.   Keep things positive and firm and calm.  Dont get mad, just do what you must to restrain this instinct for now.  If you pick her up and she struggles, hold her til she stops.  Count to 5 and then put her down.. You can lengthen the time as you go along.  I think it is a combination of instinct and fear from being separated from her siblings  and also remember, that this is the way she dealt with her siblins, right?  So she must learn how to deal with you in a calm submissive way.  
nancy

---------- FOLLOW-UP ----------

QUESTION: hey thanks for the advice.i will do as u said.i left out one thing she growls and snaps when disturbed during sleep this too only sometimes.i dunno how  shall i train her coz she doesnt even understand her name properly.?SHE HAS NOT YET STARTED EATING SOLID FOOD HOW CAN I START TRAINING HER WITH TREATS?i think the breeder have seperated this puppy from her mother when she was just 30 days!!!not crate trained not properly socialized.i am just letting you know the situation.YOU ARE DOING A VERY GREAT JOB AND I THANK YOU SINCERLY FOR YOUR ADVICERS..THANK YOU SO MUCH.

Answer
Her treat could be praise  or some soft dog food.  Even liverwurst, but be careful of that it can upset her stomach if she is not used to it so only let her lick a bit from your fingers.  But you can bet that will get her attention....
Ah she growls when you pick her up asleep,, thank you for telling me, it confirms my belief it is just puppy instinct...don't worry about her, just be firm and positive and don't frighten her and she will be fine.   She is very young to be taken away from siblings, you will have to take their place a bit....
I think she will be fine.
Let me know in a few months how she is doing
nancy