Mendel’s Law of Independent Assortment states that during the formation of gametes, different pairs of alleles segregate independently of each other. In other words, the inheritance of one trait does not affect the inheritance of another unrelated trait. This law applies to genes located on different chromosomes or genes located far apart on the same chromosome, as they assort independently.
Multiple alleles refer to the presence of more than two alleles for a particular gene in a population. A classic example is the ABO blood group system in humans, which involves three main alleles: IA, IB, and i. These alleles determine the individual’s blood type (phenotype).
Here’s a table illustrating the ABO blood group system and Rh factor:
Blood Group | Genotype | Phenotype | Antigen | Rh Blood Type |
A | IAIA | Type A | A | Positive (+) |
B | IBIB | Type B | B | Positive (+) |
AB | IAIB | Type AB | AB | Positive (+) |
O | ii | Type O | None | Positive (+) |
Rh blood type, also known as the Rhesus factor, is a protein found on red blood cells. Individuals are classified as Rh-positive (+) if they have this protein and Rh-negative (-) if they don’t. Rh factor compatibility is important during pregnancy to prevent Rh. incompatibility issues
In blood transfusion, antibodies play a critical role in determining compatibility. For individuals with blood type AB, they have both A and B antigens on their red blood cells, making them universal recipients as they lack antibodies against A and B. In the case of the Rh factor, Rh-negative individuals should receive Rh-negative blood to avoid antibody reactions. Here’s a table:
Blood Group | Blood Group Recipient | Reason |
AB | AB | Universal Recipient |
Rh+ | Rh+ | Compatible (Rh factor +) |
Rh- | Rh- | Compatible (Rh factor -) |
Rh- | Rh+ | Incompatible (Rh factor +) |
Co-dominance occurs when both alleles in a heterozygous individual express themselves fully, resulting in a combined phenotype. An example of co-dominance is seen in the human ABO blood group system, where individuals with both A and B alleles express both A and B antigens.
Incomplete dominance is observed when the heterozygous phenotype is an intermediate blend of the two homozygous phenotypes. An example is the inheritance of flower color in snapdragons, where red (RR) and white (WW) homozygotes produce pink (RW) heterozygotes.