Which of the following is not correct regarding polygenic inheritance?
1. Main mode of non-allelic genes interaction in corresponding gene series is addition of mainly small particular allele contributions.
2. The effects of allelic substitution at each of the segregating genes are usually relatively small and interchangeable which results that identical phenotype may be displayed by a great variety of genotypes.
3. The phenotypic expression of the polygenic characters is undergoing considerable modification by environmental influence.
4. Polygenic characters show a discontinuous rather than continuous distribution.