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

Which of the following statements correctly predict the results?

After one round of replication, 100% of the DNA molecules are hybrid ( $14N/15N^{14}\text{N}/^{15}\text{N}$ ).
After two rounds of replication, 50% of the DNA strands present in the population contain $14N^{14}\text{N}$ .
After three rounds of replication, the ratio of heavy-density DNA molecules ( $15N/15N^{15}\text{N}/^{15}\text{N}$ ) to intermediate-density DNA molecules ( $14N/15N^{14}\text{N}/^{15}\text{N}$ ) is $3 : 1$ .

Which of the following statements correctly predict the results?

After one round of replication, 100% of the DNA molecules are hybrid ( $14N/15N^{14}\text{N}/^{15}\text{N}$ ).
After two rounds of replication, 50% of the DNA strands present in the population contain $14N^{14}\text{N}$ .
After three rounds of replication, the ratio of heavy-density DNA molecules ( $15N/15N^{15}\text{N}/^{15}\text{N}$ ) to intermediate-density DNA molecules ( $14N/15N^{14}\text{N}/^{15}\text{N}$ ) is $3 : 1$ .

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