"Blood Group"

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Blood and blood groups are critical to understanding genetics, immunity, and inheritance patterns. Here's a breakdown:

Blood Components

  • Red Blood Cells (RBCs): Carry oxygen via hemoglobin.
  • White Blood Cells (WBCs): Fight infections.
  • Platelets: Aid in clotting.
  • Plasma: Carries nutrients, hormones, and waste.

Blood Groups and Genetics

Blood groups are determined by specific antigens on the surface of red blood cells. The most well-known systems are:

1. ABO Blood Group System

  • Controlled by the ABO gene on chromosome 9.
  • Alleles: A, B, O
    • A and B are codominant.
    • O is recessive.
  • Possible genotypes and phenotypes:
    • AA or AO → Type A
    • BB or BO → Type B
    • AB → Type AB (universal recipient)
    • OO → Type O (universal donor)

2. Rh Factor (Rhesus System)

  • Controlled by the RHD gene on chromosome 1.
  • Two alleles: Rh+ (dominant) and Rh- (recessive).
  • Rh-positive means the D antigen is present; Rh-negative means it is absent.

Genetic Inheritance of Blood Groups

  • Inheritance follows Mendelian principles.
  • Each parent donates one allele for ABO and Rh factors.
  • Example: A parent with blood type A (AO) and another with B (BO) can produce offspring with blood type A, B, AB, or O (depending on allele combinations).

Clinical Importance

  • Blood Transfusion: Matching ABO and Rh is crucial to avoid hemolytic reactions.
  • Pregnancy: Rh incompatibility between mother and fetus can cause hemolytic disease of the newborn (HDN).
  • Genetic Testing: Blood group inheritance can be used in paternity testing and forensic science.

Beyond ABO and Rh

There are over 30 blood group systems, including Kell, Duffy, Kidd, and Lewis, which can be vital for transfusions and transplantation.

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