If my blood type is O+ and my son's is O-, does that mean my son's father is O- also?

Question

If my blood type is O+ and my son's is O-, does that mean my son's father is O- also?

Answer 1

No, your son's father could be heterozygous A- or B-, and still allow for your son to be O-.

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Answer 2

Probably, but not necessarily.  At least with this scenario you don't have to worry about Rh factor problems; you would if YOU were negative and the father was positive.  

Answer 3

No.  Your son's father could have any blood type except AB+ or AB-.

You have two O alleles (oo) and are heterozygous for Rh factor, + -.  You gave your son an o allele and an Rh- allele.  The father had to also give an o allele and an Rh- allele.  But, the father could have been Ao and be type A, Bo and be type B, or oo and be type O.  The father could also have been heterozygous (like you) for the Rh factor and be positive, or he could have two Rh- alleles and be negative.