BL 100: INTRODUCTORY CELL BIOLOGY AND GENETICS
LECTURE 10: QUALITATIVE VERSUS QUANTITATIVE
INHERITANCE AND CAUSES OF VARIATION ON
PHENOTYPIC EXPRESSIONS IN GENE ACTION
,Qualitative and Quantitative genetic traits
• A qualitative trait is expressed qualitatively, which means that
the phenotype falls into different categories. The pattern of
inheritance for a qualitative trait is monogenetic, which means
that the trait is only influenced by a single gene with a major
effect.
Example: Inherited diseases caused by single mutations are
good examples of qualitative traits. Another is blood type. The
environment has very little influence on the phenotype of
qualitative traits.
• Quantitative inheritance involves traits influenced by several
genes with small effects, called polygenes, so that the
phenotypes cannot be placed in easily identifiable classes. Most
of these traits are measured on a continuous scale.
, Classification of traits in relation to mode of inheritance and
environmental tolerance
LECTURE 10: QUALITATIVE VERSUS QUANTITATIVE
INHERITANCE AND CAUSES OF VARIATION ON
PHENOTYPIC EXPRESSIONS IN GENE ACTION
,Qualitative and Quantitative genetic traits
• A qualitative trait is expressed qualitatively, which means that
the phenotype falls into different categories. The pattern of
inheritance for a qualitative trait is monogenetic, which means
that the trait is only influenced by a single gene with a major
effect.
Example: Inherited diseases caused by single mutations are
good examples of qualitative traits. Another is blood type. The
environment has very little influence on the phenotype of
qualitative traits.
• Quantitative inheritance involves traits influenced by several
genes with small effects, called polygenes, so that the
phenotypes cannot be placed in easily identifiable classes. Most
of these traits are measured on a continuous scale.
, Classification of traits in relation to mode of inheritance and
environmental tolerance
