In many paternity cases the first test involves blood typing, since blood type i
ID: 259949 • Letter: I
Question
In many paternity cases the first test involves blood typing, since blood type is an easily detected genetic trait.
A. List the different blood types. Which blood type best illustrates the concept of co-dominance?
B. List the multiple alleles at the ABO blood type gene (list the possible genotypes for each blood
type)
C. A mother with type B blood has two children, one with type A blood and one with type O.
Draw a pedigree that exemplifies the situation. What is the genotype of each of the
individuals (mother, father, and two children)?
D. In such a paternity case, a man denies fathering a child of blood type O. He is blood type AB,
while the mother is blood type O. Based on this test, could he have fathered the type O
child? Why or why not?
E. If the man were type A, and the mother type O, would the conclusion be any different? Why
or why not?
Explanation / Answer
A) There are four blood group types, which are determined by the presence or absence of two antigens.
The different blood types are A, B, AB and O. AB blood type illustrates the concept of co-dominance, which has two types of protein A and B that appear on the surface of blood cells.
B) There are 3 alleles for the gene that determines ABO blood type.
Blood type A - IAIA and IAi.
Blood type B - IBIB and IBi.
Blood type AB - IAIB.
Blood type O - ii.
C) The expected genotype of the mother - IBIB and IBi.
The expected genotype of father - IAIA and IAi.
Cross between IBi X IAi.
Gametes formed IB and i IA and i.
Next generation
Then the genotype of mother - IBi
Genotype of father - IAi
Genotype of two children - IAi and ii.
D) The genotype of father with blood type AB - IAIB.
The genotype of mother with blood type O - ii.
Cross between them IAIB X ii.
Gametes formed IA and IB i and i.
Next generation
The blood group of the child should be A or B from the test, however the blood group of child is O.Therefore the child is not from this father.
Male/Female IB i IA IAIB(Blood type AB) IAi(Blood type A) i IBi(Blood type B) ii(Blood type O)Related Questions
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