Final answer:
Traits with highly variable phenotypes that do not fall into just a few categories are called quantitative traits. These traits exhibit a continuous range of expressions and are influenced by multiple genes and environmental factors. Modern genomic techniques, such as QTL mapping, assist in identifying the genetic regions related to these traits.
Step-by-step explanation:
Traits with highly variable phenotypes that do not fall into just a few categories are known as quantitative traits. Unlike qualitative or discrete traits which have a limited number of phenotypic expressions, quantitative traits display a range of characteristics and can often be measured on a continuous scale. For instance, height, weight, and blood pressure are examples of quantitative traits because they can vary in degree and can be influenced by multiple genes as well as environmental factors.
Quantitative traits are often controlled by several genes, known as polygenic traits, contributing to the trait's expression. This complexity makes it challenging to identify the specific genetic factors, but modern genomic techniques, such as quantitative trait locus (QTL) mapping, help researchers locate the regions of the genome associated with variation in quantitative traits.