The DNA replicate itself during the S phase of interphase. If a cell undergoes meiosis with the division of DNA, it will undergo degeneration and the cell will stop its division.
Interphase is made of three main 'sub-phase' for eukaryotic cells.
G1 phase , S phase and G2 phase .
During G1 phase , the cell starts to growth and expand. Organelles such as mitochondria replicate and an enzyme/protein called cyclin is release.
Cyclin will activate the enzyme CDK (cyclin- dependent kinase) to react to the cell growth.
CDK at the end of G1 phase will be the enzyme that will decide if yes or no the cell can continue its interphase.
As an example, if there is a lack of ATP (energy) or not enough space to continue the division. CDK will stop the G1 and the cell will stay unchanged in what is called G0 phase.
Once CDK finally 'accept' the procession of growth, the cell can undergo S phase .
S-phase is extremely important as it is the time when DNA replicate .
DNA is composed of single chromatid at the point and 46 chromosomes in total (23 pairs, it is important as they get separated during meiosis I). The DNA is unwrapped at this point, and different enzyme act during replication (Helicase, RNA primers, DNA polymerase III, DNA polymerase I, DNA Ligase).
- DNA replication is a semi-conservative process - It means the new strands of DNA will be attached to old ones in a helix-shaped)
DNA will stay unwrapped until prophase I.
Once DNA is replicated, the cell undergoes G2 phase (growth phase).
BUT, at the end of interphase and during G2 phase. Cyclin is again released to activate CDK . The DNA is check, and CDK verify that the cell is ready to meiosis. If actually S-Phase did not happen, and there was no replication the CDK will never let go the cell to do meiosis.
Of course this is biology, so error might happen, but the cell meiosis will not go far without a replicated DNA, and it would result in a wrong splitting of DNA.
An interphase without S-Phase will probably result in a 'frozen' cell (Only limited activity) or a dead-cell.