Claire,
A one year old understands alot of language, even though she/he cannot say
alot of words.  A gentle reprimand and explanation that the biting hurts
Mommy would be appropriate.  Also if the baby is teething, something soothing
to the gums prior to nursing could be used.
My daughter did some biting about 10 mos old when she started cutting her
first teeth (pretty late getting teeth) but this passed quickly and at 1 yr
old now she lets go so nicely.

Laurie Wheeler, Rnc, Mn, Ibclc
Enjoying toddler nursing and all those acrobatics!