Blood Types Problem Set
Problem 3: What blood type would the father be?
Help to answer the question
If the mother of a child is blood type O+ and the child is A-, what blood type would the father be?
Does the Rh factor of the child being - mean that one of the parents has to be negative? Both of my parents are Rh - all of us siblings are Rh- as well. Could two Rh- parents give birth to a Rh+ child? and vice versa? Thanks for all your help. --MaryEllen
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Tutorial
Blood types
The father has to be the source of the A allele of a child with blood type A, when the mother is of blood type O. The father could be type A or type AB. The types that can be ruled out for the father are type O and type B.
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Mother's Possible Genotype |
Child's Possible Genotypes |
Father's Possible Genotypes |
OO |
AO |
AA, AB |
Rh factor
The Rh factor information doens't discriminate potential fathers of the child. Even though the child is Rh-, it is not necessary that either parent be Rh-.
The father of the child could be either Rh+ (heterozygous with one Rh+ allele and
one Rh- allele) or Rh- (homozygous with two recessive Rh- alleles. )
When the mother is Rh- and the father is Rh+ (heterozygous with one Rh+ allele
and one Rh- allele), there is a 50% probability for an Rh+ child and a 50%
probability for an Rh- child.
When the mother is Rh- and the father is Rh-, as in the case of your own family,
then all children (all of your siblings) will be Rh-.
Once again, if it is important to have correct and highly discriminating
information about paternity, my advice would be to explore the possibility of a
DNA-based paternity test. Although I cannot personally endorse any particular
testing company, you may wish to visit the web page of a paternity lab at
http://www.gentestlabs.com/
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The Biology Project
University of Arizona
Thursday, October 23, 1997
Contact the Development Team
http://www.biology.arizona.edu
All contents copyright © 1997. All rights reserved.
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