Given reasons for the appearance of new combination of characters in the `F_(2)` progeny in question 45.

Explanation

Appearance of new combination of characters in `F_(2)` progeny can be implicit by showing dihybrid cross, as carried out by Mendel.
Let us take up that Mendel selected pea plants with round green (RRyy) seeds, and plants with wrinkled yellow (rrYY) seeds. Let us assume that roundness and yellow colour were the dominant traits.
All the progenies in `F_(1)` generation produced round yellow seeds with genotype (RrYy) and showed dominant traits only. Though, genes for recessive traits were present in all the plants. This happened because of Law of Independent Assortment. This facilitated the combination of the trait of roundness with the trait of yellow colour, although these traits came from different parents.
In the `F_(2)` generation, recombination of traits took place once again in accordance with the Law of Independent Assortment.
During Mendel.s experiment with dihybrid cross, it was seen that all the plants in `F_(1)` generation produced round and yellow seeds. However, in `F_(2)` generation, phenotypes of different seeds were different. This shows new combination of characters in `F_(2)` generation.
Because of this, the `F_(2)` generation showed different combinations of genotype, namely, RRYY, RRYy, RrYY, RrYy, rrYY, rrYy, rryy.