Answer
For another round of replication, there should be proportionally more light double helices--the upper band in the centrifuge tube should become darker. The band of intermediate weight (half light, half heavy) should remain the same.
Work Step by Step
The number of mixed-weight strands remains constant because the heavy strands are not destroyed, but no new ones are made in the light/14N medium. More and more light strands are made, leading to more light double helices, and a darker band for the lighter helices, which is the upper band in the centrifuge tube.
