Blood Group Genetics Quiz

History of Blood Transfusion

• In 1667, Jean Baptiste Denys conducted the first animal-to-human blood transfusion using lamb's blood, leading to initial apparent success.
• The third transfusion resulted in the death of the young man, revealing severe risks associated with cross-species transfusions.
• Animal blood transfusions were banned from 1667 to 1818 due to repeated failures and adverse reactions.
• James Blundell successfully performed human-to-human transfusions in the early 19th century, targeting women experiencing childbirth hemorrhages.
• Early species-specific transfusions had a 50% survival rate but often resulted in fatal outcomes.
• Karl Landsteiner's discovery of ABO blood groups in 1900 explained many transfusion incompatibilities linked to red cell antigens.
• Landsteiner identified unique antigens on red cells, concluding that each species carries distinct and some shared factors.

Blood Group Genetics

• Human cells possess 46 chromosomes arranged in 23 pairs, with genes contained on these chromosomes influencing inherited traits.
• Genetic material is housed in DNA within the nucleus of every cell.
• Mitosis ensures body cells replicate while maintaining 46 chromosomes, whereas meiosis produces sex cells containing 23 chromosomes.
• The fertilized ovum receives 23 chromosomes from each parent, totaling 46 chromosomes which arrange in pairs.
• Homozygous individuals inherit identical alleles from both parents, while heterozygous individuals have different alleles.

Phenotype versus Genotype

• Phenotype reflects the observable traits manifested in an individual, while genotype denotes the underlying genetic makeup.
• Hemagglutination is used to determine a patient's phenotype, with blood type tested against specific antisera.
• A person with no agglutination from anti-A or anti-B antisera is classified as blood type O, but may have either A/A or A/O genotype.

Punnett Square

• A Punnett square predicts genotype probability in offspring by summarizing potential allele combinations from parents.

Genes and Alleles

• Genes are the fundamental hereditary units on chromosomes, with specific sites called loci.
• Alleles represent alternative forms of a gene, and antigens produced by opposing alleles may be antithetical.

Population Genetics

• Genotype and phenotype occurrences can be analyzed through specific formulas including the Hardy-Weinberg Principle.
• Phenotype calculations help identify red blood cells with particular antigen characteristics.
• Example: Approximately 10% of a population may be negative for all three of selected antigens.

Hardy-Weinberg Formula

• Represents allele frequencies with the equation p + q = 1 (p = frequency of one allele; q = frequency of the other).
• Genotype proportions are calculated using (p + q)² = 1.0, providing breakdowns for homozygous and heterozygous forms.

Role of H-Gene in ABO Gene Expression

• The inheritance of A and B genes typically leads to the expression of respective antigens on erythrocytes.
• H, A, and B antigens derive from specific enzymes coded by corresponding genes, with A and B gene products emerging indirectly.