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Inheritance of Blood Groups in Humans

Edumaps Wissen

🧬 Genetic Basics of Blood Groups

  • The most commonly used blood group system in humans is the ABO system (“A B Zero”).
  • There are three different alleles: A, B, and 0 (Zero).
  • Every person receives one of these alleles from each parent, making two in total. The combination of these alleles determines the blood group.
  • Possible genotypes are:
    • AA or A0 → blood group A
    • BB or B0 → blood group B
    • AB → blood group AB
    • 00 → blood group 0
  • This fundamental classification is important for understanding inheritance and transfusion compatibility.
  • ⚙ grundlagen
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🧬 Dominant & Recessive: What Does That Mean?

  • In the ABO system, there are dominant alleles and recessive alleles:
    • The alleles A and B are codominant. This means both features are fully expressed in the genotype AB – that person has blood group AB.
    • The allele 0 is recessive. It only appears in the blood group if both inherited alleles are 0 (genotype 00).
  • Examples:
    • A parent with genotype A0 can pass on either A or 0.
    • A parent with genotype B0 can pass on either B or 0.
  • The expression of the blood group can be clearly explained by dominance and codominance.
  • ⚙ dominant
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🧩 Punnett Square: Example Blood Group Combinations

  • The Punnett square is a practical tool for predicting possible blood groups of offspring.
  • Example: One parent has genotype A0, the other has B0.
  • B 0
    A AB A0
    0 B0 00
  • Evaluation:
    • 25% probability for blood group AB (AB)
    • 25% for blood group A (A0)
    • 25% for blood group B (B0)
    • 25% for blood group 0 (00)
  • ⚙ punnett
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👨👩👧👦 Blood Group Inheritance in the Family

  • The blood groups of children can be determined precisely based on the parents’ alleles. There are some interesting possibilities and also limitations.
  • Two parents with blood group 0 (00 and 00) can only have children with blood group 0.
  • When both parents have blood group AB (AB and AB), their children can only have blood groups A, B, or AB, but never 0.
  • Inheritance follows fixed rules and can be clearly illustrated with the Punnett squares.
  • Important terms:
    • "Homozygous": Two identical alleles (e.g., AA, 00)
    • "Heterozygous": Two different alleles (e.g., A0, AB)
  • ⚙ vererbung
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💡 Summary & Significance

  • The inheritance of blood groups is based on the three alleles A, B, and 0, where A and B are codominant and 0 is recessive.
  • The parents’ gene combinations clearly determine their children’s blood groups.
  • Punnett squares help visualize the probabilities.
  • Understanding blood group inheritance is important for medical questions, such as blood transfusions or paternity tests, and shows how classic genetics work in humans.
  • ⚙ zusammenfassung
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Distribution of Blood Groups in the Population

  • The distribution of blood groups differs by region and population group. In Germany, the percentage distribution looks approximately as follows:
  • Blood Group Share of Population
    0+ approx. 35 %
    A+ approx. 37 %
    B+ approx. 9 %
    AB+ approx. 4 %
    0− approx. 6 %
    A− approx. 6 %
    B− approx. 2 %
    AB− approx. 1 %
  • Blood groups are especially important in blood transfusions and emergency medicine.
  • ⚙ verteilung
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