Question

Mono hybrid and di hybrid cross explanation with example.

Answer 1

monohybrid : one pair of contrasting character, eg. red coloured flowers and white coloured flowers
dihybrid: two pair of contrasting character,
eg. round and yellow coloured seeds and wrinkled green coloured seeds

Answer 2

in mono hybrid cross we only talk abt only one trait take an example of pea plant and the trait is height i.e one short pea plant and one tall pea plant

take tall as TT and short is tt (remember TT  is pure tall)
so when mendal cross breed TT and tt everyone thought the next progeny will be medium in height but it would not be medium and it would ne tall instead with Tt which is heterogeneous tall
so but when he self pollinate Tt plant he got TT ,Tt ,Tt,tt
so the genotypic ratio of F2 progeny is 1:2:1
and the phenotypic ratio is 3:1

In di hybrid cross we will take two traits i.e their color and size
take round green as RRyy and wrinkled yellow as rrYY
when he cross breed them he got RrYy  and  in F2 generation he got 16 results in which 9 are round yellow 3 are round green
 3 are wrinkled yellow and 1 is wrinkled  green ( note that the heterozygous condition is also called hybrid). the genotypic ration of di hybrid pea plant is 1:2:2:4:2:2:1:1:1 and the phenotypic ratio is 9:3:3:1