The $F_2$ dihybrid ratio $9 : 3 : 4$ is explained on the basis of

In which plant was the lethal gene first observed?

Read all the given statements carefully and determine the number of correct statements.
$(1)$ Mutations are not hereditary.
$(2)$ Male $Drosophila$ flies do not show crossing over.
$(3)$ In honeybees,the male bee is diploid.
$(4)$ In a frame-shift mutation,one nitrogen base is replaced by another nitrogen base at a specific position.
$(5)$ Genes are responsible for inheritance.

What is true for the expression of recessive characters?

In bread wheat,the chromosome number is:

Which of the following statements are correct?
$(a)$ The $X$-linked genes are located on the non-homologous region of $X$-chromosomes.
$(b)$ Females with the recessive gene on one $X$-chromosome are carriers.
$(c)$ The carrier female is also severely affected by the disorder.
$(d)$ $Y$-linked genes are located on the homologous region of $Y$-chromosome.
$(e)$ Human males have homomorphic sex chromosomes.
Choose the correct option.