BRAINCAKEPolygenic Traits
Some characteristics are controlled by a single gene (monogenic). These usually show discontinuous variation: individuals fall into a few distinct categories with no intermediates, for example blood group or pea seed shape.
Many characteristics are polygenic: they are controlled by several genes at different loci, often on different chromosomes. Examples include human height, skin colour and milk yield in cattle. Each gene has a small, additive effect on the phenotype.
Polygenic traits show continuous variation. Because many combinations of alleles are possible, there is a range of phenotypes with no clear categories. When the frequencies are plotted, the data usually form a normal distribution (a bell-shaped curve), with most individuals near the mean.
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More in Genetic Information
- Different Types of Mutation
- Random Fertilisation
- Genetics and Inheritance
- Alleles
- Monohybrid Crosses
- Test Cross
- Sampling Errors
- Mendel
All 30 lessons in Genetic Information · All Edexcel A-level Biology topics