A parent DNA molecule with both strands labeled with heavy nitrogen (${}^{15}N$) is transferred to a growth medium containing only light nitrogen (${}^{14}N$) and allowed to undergo three rounds of replication.

Which of the following statements correctly predict the results if DNA replication is semiconservative?

1. After one round of replication, 100% of the DNA molecules have an intermediate hybrid density (${}^{15}N{/}^{14}N$).
2. After two rounds of replication, there is an equal proportion of intermediate density (${}^{15}N{/}^{14}N$) molecules and light density (${}^{14}N{/}^{14}N$) molecules.
3. After three rounds of replication, 75% of the DNA molecules have intermediate hybrid density (${}^{15}N{/}^{14}N$) and 25% have light density (${}^{14}N{/}^{14}N$).