The modified allele could be responsible for the production of which of the following?

Mendel published his work on the inheritance of characters in $1865$,but it remained unrecognized until $1900$ because:
$(a)$ He could not provide any physical proof for the existence of factors.
$(b)$ His concept of factors as stable,discrete units that controlled the expression of traits did not find acceptance from his contemporaries.
$(c)$ Mendel's approach of using mathematics to explain biological phenomena was considered ahead of its time and unconventional.
$(d)$ Communication was not easy (as it is now),and his work could not be widely publicized.

Mendel was lucky, because

Different forms of genes that represent the same trait are called ....

According to Mendel, which of the following traits represents a recessive character?

What is represented by the following cross?
$Tt \times tt$