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Biology 2nd Baccalaureate

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Inheritance of a character. Rh blood groups. (Page 3)

Regardless of whether we have blood group A, B, AB or 0, we have a positive or negative Rh factor depending on the characteristics of the blood.

The Rh factor is determined by an antigen. If we have a protein (D antigen) on the surface of red blood cells, its Rh factor will be positive , and if we do not have it, its Rh factor will be negative. Most people (85%) are Rh positive.

The presence of the D antigen (or Rh factor) is determined by a gene found on chromosomes of pair 1. This gene has two alleles, D and d.

  • D is responsible for the existence of the D antigen and, therefore, for the individual to be Rh+. It is dominant over the d.
  • d prevents the antigen from being formed, so it will determine Rh-, as long as D is not present, since d is recessive with respect to D.

In the section that we have devoted to the solved problems of AB0 blood groups, you will also find problems in which the Rh blood group appears, so we could have also placed them within the group of inheritance problems of two characters.

Genetics problem 17

Can an Rh positive man have a child with an Rh positive woman who is Rh negative?

Genetics problem 18

A woman, the daughter of Rh positive parents, is Rh positive.  Can you have an Rh negative child if your partner is Rh negative?


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