* Chromosomes and DNA: Each chromosome is made up of one DNA molecule.

* G2 Phase: During the G2 phase of the cell cycle, DNA has already been replicated. This means each chromosome now consists of two identical sister chromatids, still joined together.

Calculations:

1. Pairs of chromosomes: The animal has 6 pairs of chromosomes, which means it has 6 * 2 = 12 individual chromosomes.

2. DNA molecules after replication: Since each chromosome is duplicated during G2, there are now 12 * 2 = 24 DNA molecules.

Answer: There are 24 DNA molecules present in the nuclei of these animals during G2 phase.