. A woman whose father was color blind (X-linked, recessive) and who has type A blood has accused a man who is himself color blind of fathering her child. The accused man has type B blood. For each of the following cases, indicate whether or not the man might be the father. Explain your answer by including the genotype of the child and demonstrating how that genotype could be produced.
a) a color blind son with type O blood
b) a normal visioned son with type O blood
c) a normal visioned son with type AB blood
d) a color blind daughter with type B blood
e) a normal visioned daughter with type A blood
a) Remember that the colorblind gene is sex-linked, on the X chromosome. Whenever the male has that chromosome, he is color blind.
b) Did the woman or her father have type A blood? If the woman and the accused father both had recessive O genes, it is possible.
c) this is also possible. Do a Punnett square with AO and BO blood types respectively.
d) Do Punnett square with colorblind gene and AO/BO.
e) Do Punnett square with colorblind gene and AO/BO.
To determine whether the accused man could be the father in each of the given cases, we need to consider the genetic inheritance patterns for both color blindness and blood type. Let's go through each case and explain how to determine whether he could be the father.
a) In this case, the child is a color blind son with type O blood. Since the woman's father was color blind, we know she is a carrier for the trait. Therefore, she could pass the color blindness allele to her son. The man being accused is also color blind, so he could pass the color blindness allele to the child as well. In order for the child to have type O blood, both parents must contribute an O blood type allele. Therefore, the child's genotype could be XbXb (color blind) and ii (O blood type). The accused man could be the father in this case.
b) Here, the child is a normal-visioned son with type O blood. Since the woman's father was color blind, we know she is a carrier for the trait. However, the accused man is also color blind, so he cannot contribute a dominant allele for normal vision. As a result, the child cannot have normal vision unless the mother has an additional copy of the dominant allele for normal vision. Therefore, the child's genotype could be XbXb (color blind) and ii (O blood type). The accused man is unlikely to be the father in this case.
c) In this case, the child is a normal-visioned son with type AB blood. Since the woman has type A blood, the child must have inherited an A blood type allele from her. However, the accused man has type B blood, so he cannot contribute an A blood type allele. Therefore, the child cannot have type AB blood unless the mother has an additional copy of the B blood type allele. The child's genotype could be XbY (color blind) and IAIB (AB blood type). The accused man is unlikely to be the father in this case.
d) Here, the child is a color blind daughter with type B blood. Since the woman's father was color blind, we know she is a carrier for the trait. The child's genotype could be XbXb (color blind) and IBi (B blood type). Since the accused man is color blind, he could pass the color blindness allele to the child. The accused man could be the father in this case.
e) In this case, the child is a normal-visioned daughter with type A blood. Since the woman has type A blood, the child must have inherited an A blood type allele from her. The child's genotype could be XBXB (normal visioned) and IAi (A blood type). However, the accused man has type B blood, so he cannot contribute an A blood type allele. Therefore, the child cannot have type A blood unless the mother has an additional copy of the B blood type allele. The accused man is unlikely to be the father in this case.
In summary:
a) The accused man could be the father.
b) The accused man is unlikely to be the father.
c) The accused man is unlikely to be the father.
d) The accused man could be the father.
e) The accused man is unlikely to be the father.