Nicotiana sylvestris flowers only during long days and $N$.tabacum flowers only during short days, if raised in the laboratory under different photoperiods, they can be induced to flower at the same time and can be cross fertilized to produce self-fertile offspring. What is the best reason for considering $N .$ sylvestris and $N$. tobaccum to be separate species?

Some individuals with blood group -$A$ may inherit the genes for blonde hair, while other individuals with blood group -$A$ may the gene for brown hair. This can be best explained by the principle of

Cytoplasmic inheritance always shows

Mendel's law were first published in the year

Cytoplasmic male sterility in maize is manifestation of interaction between