Examkin

Question

Difficulty: MediumContinuous and Discontinuous Variation

Human blood groups under the ABO system represent continuous variation because they display a smooth spectrum of intermediate phenotypes influenced by environmental factors.

Answer: Answer

Answer

The statement is false because ABO blood groups exhibit discontinuous variation, characterized by distinct non-overlapping categories controlled by a single gene with no environmental influence.
The statement is false because human ABO blood grouping is a classic example of discontinuous variation. Individuals belong to distinct, non-overlapping phenotypes (A, B, AB, or O) determined strictly by monogenic inheritance without environmental modification.

Step-by-Step Solution

1
Analyze the nature of the phenotypic distribution of human ABO blood groups.
Individuals fall strictly into one of four distinct categories: A, B, AB, or O, with no intermediate blood types.
Traits showing discrete, non-overlapping categories represent discontinuous variation rather than a continuous spectrum.
2
Evaluate the underlying genetic mechanism and environmental impact on the trait.
ABO blood grouping is inherited monogenically via codominant and recessive alleles (IAI^A, IBI^B, ii) and cannot be altered by environmental factors.
Discontinuous traits are typically controlled by one or two major genes and are not subject to environmental modifications.
3
Determine the accuracy of the given statement.
The statement incorrectly describes ABO blood groups as continuous and environmentally influenced.
Continuous variation applies to polygenic traits like height and skin color which show a normal distribution curve, making the premise false for blood groups.

Key Concept

Discontinuous variation involves distinct, non-overlapping phenotypic categories controlled by one or a few genes with no environmental influence, whereas continuous variation presents a wide spectrum of intermediate forms controlled by polygenes and influenced by environmental factors.
Estimated Time:1m 0s
Rate this question

Topics

Continuous and Discontinuous Variation

More questions from this topic