Match each human variation trait on the left with its correct genetic, morphological, or p… — JAMB UTME

Match each human variation trait on the left with its correct genetic, morphological, or physiological classification on the right.

Sickle-cell hemoglobin status ( $Hb^A / Hb^S$ )Discontinuous physiological variation exhibiting codominance and selective advantage against malaria
PTC (Phenylthiocarbamide) tasting sensitivityDiscontinuous physiological variation determined by monogenic Mendelian inheritance of chemical taste perception
Total fingerprint dermal ridge countContinuous morphological variation displaying polygenic inheritance that is unalterable by post-natal environment
Human skin melanin concentrationContinuous morphological variation displaying polygenic additive inheritance subject to environmental phenotypic modification

Answer

Sickle-cell status matches discontinuous physiological variation with codominance and malaria advantage; PTC tasting sensitivity matches discontinuous physiological variation determined by monogenic taste perception; Total fingerprint dermal ridge count matches continuous morphological variation under polygenic control unaffected by post-natal environment; Skin melanin concentration matches continuous morphological variation under polygenic control with environmental modification.

The correct pairing matches each human variation according to whether it affects physical anatomy (morphological) or internal biological function (physiological), whether it shows continuous quantitative distribution or distinct categorical groups (discontinuous), and its specific mode of genetic control and environmental interaction.

Step-by-Step Solution

Distinguish between morphological and physiological variations

Sickle-cell hemoglobin status and PTC taste perception involve internal cellular biochemistry and chemoreception (physiological traits). Fingerprint ridge count and skin color involve outward structural and physical features (morphological traits).

Morphological traits describe anatomical form, whereas physiological traits describe internal function and biochemical processes.

Differentiate between continuous and discontinuous variation distributions

Sickle-cell status and PTC tasting split individuals into distinct, non-overlapping phenotypic groups (discontinuous variation). Fingerprint ridge counts and skin melanin levels form a smooth gradient of continuous numerical values across a population (continuous variation).

Discontinuous traits are controlled by one or few genes with major effects, while continuous traits are quantitative and governed by polygenes.

Determine specific genetic inheritance and environmental influences

Sickle-cell status involves codominance (

Hb^A

and

Hb^S

) providing heterozygote protection against malaria. PTC tasting follows monogenic Mendelian inheritance. Fingerprint ridge counts are polygenic yet unaffected by post-natal factors, while skin color is polygenic and modified by environmental UV radiation.

Each variation combines distinct modes of gene expression (monogenic vs polygenic, codominance) and environmental susceptibility.

Key Concept

Classification and underlying mechanisms of human morphological and physiological variations

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