Mendel did not study common, naturally occurring phenotypes

Modern genetics research increasingly reveals that what is commonly termed Mendelian genetics occurs rarely in nature, especially with regard to the effects that genetic variation exerts on human characteristics. It has been argued that an inappropriate emphasis on Mendel's work could distort the public understanding of genetics and indeed in the UK Mendel has been completely dropped from the official school syllabus. There is a widespread misunderstanding that Mendel studied common phenotypes such as height and colour in individual pea plants. In fact, he studied a handful of specially selected phenotypes which he observed to be always dichotomous in 22 specially bred varieties of pea and studied crosses between individuals from these different varieties. This approach enabled him to study a small number of phenotypes which did in fact exhibit truly Mendelian transmission. Modern molecular genetic studies have now demonstrated that these phenotypes result from loss of function variants which result in markedly reduced activity of specific proteins and which hence have recessive effects. Understanding that Mendel studied the effects of loss of function mutations in crosses between artificially bred varieties, rather than naturally occurring variation in a population, could allow his work to continue to be taught as part of a modern genetics curriculum.