In a famous experiment, matthew meselson and franklin stahl grew e. coli cells in a medium containing only the "heavy" isotope of nitrogen, n15 . these cells were then transferred to a medium with the "light" isotope of nitrogen, n14 . the results of the experiment supported the hypothesis of semiconservative replication, which was proposed by watson and crick. heavy dna ( n15 dna), hybrid dna, and light dna ( n14 dna) can be separated by centrifugation. if cells containing n15 dna are transferred to a medium with only n14 nh4cl as a nitrogen source, what percent of daughter molecules are composed of hybrid dna after 3 generations?

The two naturally occurring isotopes of chlorine are 35cl (34.969 amu, 75.77%) and 37cl (36.966 amu, 24.23%). the two naturally occurring isotopes of bromine are 79br (78.918 rm amu, 50.69%) and 81br (80.916 amu, 49.31%). chlorine and bromine combine to form bromine monochloride, brcl. 1. how many peaks will be present in a mass spectrum for brcl? the four combinations of molecule possible given these four isotopes are: 81br37cl, 81br35cl, 79br37cl, and 79br35cl. 2. what are the masses of the four different brcl molecules? express the masses using six significant figures, in decreasing numeric order (highest to lowest), separated by commas.