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3.5.6.1 AB0 blood groups (problems solved)

Codominant inheritance. Blood groups AB0. (Page 24)

You can practice with this simulator discovering what the phenotype and genotype of the children of two people who have a certain genotype can be like. It will help you understand how codominance problems are done.

Nomenclature for genetic problems

In multiple allelism problems , the character is determined by more than two alleles for a gene. The most typical example is the AB0 system blood group. Each individual presents in his genotype only two of the possible alleles. To make this idea clear, a nomenclature will be used in which all the alleles for that gene are represented using the same letter (I), and differing in the superscripts (IA, IB, I0) or subscripts IA, IB, I0). The allele I0 can also be represented by i to express its recessiveness with respect to the other two.

Remember that the number 0 is not the letter O.

Genetics problem 169

Blood groups in the human species are determined by three allele genes: IA, which determines group A, IB, which determines group B and i, which determines group 0. Genes IA and IB are codominant and both they are dominant with respect to gene i, which is recessive. 

How can they be the children of a group 0 man and a group AB woman? 

Genetics problem 170

A couple in which the woman belongs to group 0 Rh- and the man is AB Rh+ claim as theirs a baby whose blood is A Rh+. What would you think as a judge about this lawsuit?

Genetics problem 171

Blood groups in the human species are determined by three allele genes: IA, which determines group A, IB, which determines group B and i, which determines group 0. Genes IA and IB are codominant and both they are dominant with respect to gene i, which is recessive.

How can they be the children of an AB group man and AB group woman?

Genetics problem 172

Blood groups in the human species are determined by three allele genes: IA, which determines group A, IB, which determines group B and i, which determines group 0. Genes IA and IB are codominant and both they are dominant with respect to gene i, which is recessive. 

How can they be the children of a man from group A, whose mother was from group 0, and a woman from group B, whose father was from group 0? Make a well-done crossbreeding scheme

Genetics problem 173

A woman with blood group 0 has had a child with blood group A. What is the child's genotype? And the phenotype of the father?

Genetics problem 174

Two men (Father 1 and Father 2) claim in court the paternity of a child, whose blood group is 0. The mother is from group A, while the possible father 1 is from B and the possible father 2 is from AB. Please explain if this information can be used to indicate which of them is not your father. Come up with possible genotypes for the child, mother, and parents.

Genetics problem 175

A woman with blood group A and a man with blood group B have a child with blood group 0. What is the genotype of the parents?

Genetics problem 176

What is the probability that a couple with blood group AB and 0 will have a child of blood group A? What is the possibility that the child has blood group 0?

Genetics problem 177

Two men (Father 1 and Father 2) claim in court the paternity of a child, whose blood group is 0. Regarding their phenotypes, we know that the mother is from group A, while the possible father 1 is from group B and possible parent 2 is from group 0. 

a) Propose all possible genotypes for the child, mother and parents.

b) Reason if this information can be used to indicate which of them is not their father.

Genetics problem 178

A man with blood group A marries a woman of group B and they have a child of group A. 

a) List all the possible genotypes of these three people?

b) What genotype would the parents have if they had had a child from group 0? In this case, what other genotypes and how often could be expected in the offspring?