Give a genetic explanation for the following cross. When a tall pea plant with rounds seeds was

Give a genetic explanation for the following cross. When a tall pea plant with rounds seeds was crossed with a dwarf pea with wrinkled seeds then all the individual of `F_(1)`-populations were tall with round seeds. However selfing among `F_(1)`-population led to a 9:3: 3:1 Phenotypic ratio.

seeds