If a hybrid DNA molecule (represented as 14N 15N) is allowed to replicate twice in normal culture medium, the percentage of hybrid DNA will be :

The hybrid DNA is represented as N14N15. When this DNA is replicated twice in a normal medium then after the first replication there will be production of one normal DNA and one hybrid DNA. When these DNA molecules are replicated again in a normal medium then there will be the production of three normal DNA molecules and one hybrid DNA molecule. Therefore the percentage of hybrid DNA molecule will be 25%.