Question

Which of the following characteristics represents ‘the inheritance of blood groups in humans?

$\mathrm{i})$ Dominance.
$\mathrm{ii})$ Codominance.
$\mathrm{iii})$ Multiple alleles.
$\mathrm{iv})$ Incomplete dominance.
$\mathrm{v})$ Polygenic inheritance.

• A. $\mathrm{ii},\mathrm{iii},\mathrm{v}$
• B. $\mathrm{i},\mathrm{iii},\mathrm{v}$
• C. $\mathrm{ii},\mathrm{iv},\mathrm{v}$
• D. $\mathrm{i},\mathrm{ii},\mathrm{iii}$

Answer 1

The correct option is D

$\mathrm{i},\mathrm{ii},\mathrm{iii}$

The correct option is D.

Explanation of correct option:

1. Inheritance in the human blood group shows multiple alleles, dominance, and codominance.
2. The inheritance is determined by three alleles, ${\mathrm{I}}_{\mathrm{A}}$, ${\mathrm{I}}_{\mathrm{B}}$, and ${\mathrm{I}}_{\mathrm{O}}$.
3. The gene is present in two forms; one is dominant ( ${\mathrm{I}}_{\mathrm{A}}$ or ${\mathrm{I}}_{\mathrm{B}}$) and the other is the recessive form (${\mathrm{I}}_{\mathrm{O}}$ or i).
4. The blood group is fully expressed, when present in allele pairs.

Example:

1. ${\mathrm{I}}_{\mathrm{A}}$${\mathrm{I}}_{\mathrm{A}}$ or ${\mathrm{I}}_{\mathrm{A}}$${\mathrm{I}}_{\mathrm{O}}$ : Blood group A
2. ${\mathrm{I}}_{\mathrm{B}}$${\mathrm{I}}_{\mathrm{B}}$ or ${\mathrm{I}}_{\mathrm{B}}$${\mathrm{I}}_{\mathrm{O}}$ : Blood group B
3. ${\mathrm{I}}_{\mathrm{A}}$${\mathrm{I}}_{\mathrm{B}}$ : Blood group AB
4. ${\mathrm{I}}_{\mathrm{O}}$${\mathrm{I}}_{\mathrm{O}}$ : Blood group O

Explanation of incorrect options:

Option(A):

Blood group inheritance is an example of codominance and multiple alleles, but it is not determined by polygenic inheritance.

Option(B):

Blood group inheritance is represented by dominance and multiple alleles, but it is not determined by polygenic inheritance.

Option(C):

1. Inheritance of the blood group is a genetic phenomenon of dominance, codominance, and multiple alleles.
2. Polygenes and polygenic inheritance have no role in it.
3. The expression of phenotype is only possible when both the alleles are expressed together; hence incomplete dominance is not possible for determining the blood group.

Final Answer: Dominance, codominance, and multiple alleles represent the inheritance of blood groups in humans.