There are two types of pea plants according to Mendel: 1)Tall(TT or Tt) 2)Dwarf(tt) But I have a doubt! Is there a heterogeneous dwarf pea plant(tT)? When there can exist a heterogeneous tall pea plant, there must exist a heterogeneous dwarf pea plant also! This doubt is troubling me very much! Please clear my doubt!
there must exist a heterogeneous dwarf pea plant also. I don't understand why you think it must be the case.
Under this simple genetic model, there is no environmental variance and
T is dominant over
t is therefore recessive) and therefore the heterozygotes
Tt have the same phenotype than the homozygote
TT. There is no
Tt individuals that have the same phenotype as
t was dominant, then
Tt individuals would have the same phenotype as
tt individuals. If
t were perfectly additive, then
Tt individuals would have a phenotype half way between the
TT and the
tt phenotypes (
Tt would be of average height).
Please note, that very few real life cases are that easy. There is often interaction between many loci and there is often (if not always) environmental influence on the phenotype.