C because i look up what is what and found the same questions your welcome
Answer:
50%
Explanation:
DNA replication is a semi-conservative process. It means that after DNA replication, the newly formed DNA molecules have one parental strand and one newly formed strand. The cells in the experiment have DNA with 15N. After one round of DNA replication, each DNA molecule would have one parental DNA strand with 15N and one newly formed DNA strand with 14N.
However, after the second round of DNA replication, each hybrid DNA with strand having 15N and the other with 14N would be unwound. The parental heavy DNA strands would be present in the 50% of the newly formed DNA while the rest 50% of DNA molecules would have both strands with 14N (both light strands).
The model is called a double helix because two long strands twist around each other like a twisted ladder. The rails of the ladder are made of alternating sugar and phosphate molecules. The steps of the ladder are made of two bases joined together with either two or three weak hydrogen bonds.
