Meselson and stahl cultured e. coli for several generations in a medium with a heavy isotope of nitrogen, 15n. they transferred the bacteria to a medium with a light isotope of nitrogen, 14 n. after two rounds of dna replication, half the dna molecules were light (both strands had 14n) and half were hybrids (15n-14n). what did the researchers conclude from these results? meselson and stahl cultured e. coli for several generations in a medium with a heavy isotope of nitrogen, 15n. they transferred the bacteria to a medium with a light isotope of nitrogen, 14 n. after two rounds of dna replication, half the dna molecules were light (both strands had 14n) and half were hybrids (15n-14n). what did the researchers conclude from these results? dna replication is semiconservative. opposite dna strands are complementary to each other. the nitrogenous bases in dna molecules incorporate both 15n and 14n.

Meselson and Stahl concluded that DNA replication is semiconservative.

Semi-conservative type of replication refers to replication of DNA molecule in which newly formed DNA molecule contains one new and one old strand. During the replication, two strands of DNA unwind from each other (enzyme helicase), and each of them acts as a template for synthesis of a new, complementary strand. So, as a result, two DNA molecules that are formed are with one original strand and one new strand.

Mechanism shown by this experiment is today universal mechanism of replication, shared by all organisms on the world.

the reason the two sea urchins don't compete with each other for food, resources, etc. is because the urchins have adapted to the environment but they have also adapted to each other. this is most likely because the genes of the sea urchins.

the answer is c) abandoned properties that are contaminated with hazardous materials.