In a plant with genotype $RrYy$,if self-pollination occurs,what will be the ratio of the following genotypes: $RRYY, RrYY, RRYy, RrYy$?

Define/Explain: Dihybrid cross.

During a dihybrid cross with contrasting characters,in the $F_2$ generation,what is the proportion of individuals with parental genotypes (in $/6$)?

$A$ human male is heterozygous for autosomal genes $A$ and $B$ and is also hemophilic (gene $h$). What proportion of his sperm will contain the $abh$ gene combination?

In plants,red fruit $(R)$ is dominant over yellow fruit $(r)$ and tall height $(T)$ is dominant over dwarf height $(t)$. If a plant with genotype $RRTt$ is crossed with a plant with genotype $RRTt$,what will be the phenotype of the offspring?

When a cross is made between a tall plant with yellow seeds $(TtYy)$ and a tall plant with green seeds $(Ttyy)$,what proportions of phenotypes in the offspring could be expected to be:
$(a)$ Tall and green.
$(b)$ Dwarf and green.