When breeding an RR to another RR: 
All lambs will be RR. 

When breeding an RR to a QR: Each lamb has a 
50% chance of being RR
And a 50% chance of being a QR
And a 0% chance of being QQ 

When breeding an RR to a QQ: Each lamb has a 
100% chance of being a QR
0% chance of being a RR
0% chance of being a QQ 

When breeding a QR to a QR: Each lamb has a 
50% chance of being a QR
And a 25% chance of being an RR
And a 25% chance of being a QQ 

When breeding a QQ to a QQ: 
All lambs will be QQ 

When breeding a QQ to a QR: Each lamb has a 
50% chance of being a QR
And a 50% chance of being a QQ
And a 0% chance of being a RR 