No. You can build unending loops (infinite loops)
with it.
But additional instructions are needed for  
while loops
and for if-then-else structures.
A conditional branch instruction
branches to a new address only if a
certain condition is true.
Usually the condition
is about the values in registers.
Here is the
 beq 
(branch on equal) instruction:
beq  u,v,addr   # if register $u == register $v
                #     PC  <-- addr (after a delay of one machine cycle.)
                # else
                #     no effect.
The bit patterns in two registers are compared. If the bit patterns are the same, the PC is changed to the branch address. There is a branch delay following the instruction (just as for a jump instruction).