Mendelian inheritance in humans is difficult to study. Current understanding of mendelian inheritance in humans is gained by analysis of family pedigrees or the results of matings that have already occurred. By analysing a pedigree, we may be able to predict how the trait is inherited.
It is a visual tool for documenting the biological relationship in families and to determine the mode of inheritance (dominant, recessive, etc.,) of genetic diseases.
Whereas quantitative trait, polygenic trait and maternal traits are not studied by pedigree analysis.
Continuous traits are often measured and given a quantitative value, they are often referred as quantitative traits, e.g., crop yield, weight, gain in animals, IQ, etc.
Polygenic traits are another exception to Mendels rule, which occurs when a trait is controlled by more than one gene. This means that each dominant allele adds to the expression of the next dominant allele.
Maternal traits are the traits inherited and expressed from the maternal parent to the subsequent off springs.