In semi-conservative replication, the new molecule of DNA has one strand from the original molecule and one new strand produced from nucleotides in the surrounding environment. How does generation 1 support this model?

In the semi-conservative replication, two DNA molecules originate, each composed of a strand of the original DNA and a new complementary strand. In other words, DNA is formed from an old and a new strand. In other words, the existing threads serve as a complementary mold to the new ones.

The Meselson-Stahl experiment consists in growing the Escherichia coli bacteria in a medium that contains heavy nitrogen (Nitrogen-15 that is heavier than the most common isotope: Nitrogen-14). The first generation of bacteria was grown in a medium containing only N-15 as a source of N. The bacterium was then transferred to a medium with N-14. Watson and Crick had predicted that DNA replication was semi-conservative, if so the DNA extracted from the bacteria after cultivation for a generation in N-14 would have an intermediate weight between the DNA extracted from the medium with N-15 and that extracted. on average with N-14 and so it was.

This is how it was shown that generation 1 supports the semi-conservative replication model.

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