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Semi conservative model of DNA Replication Cheat Sheet (DRAFT) by

The two strand would separate and acts as a template for the synthesis of new complementary strands. This was termed as Semiconservative DNA replication.

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Messelson and Stahl's Experi­ment( Heavy Nitrogen)

Bacteria species Escher­ichia coli.
Culture = N15 isotopes i.e. heavy nitrogen.
After replicated for few genera­tions both strands have N15.
*When N15 bacterias were transf­erred to N14 medium, it was found that DNA separate from fresh generation possess one strand heavier.
*The heavier strand represents parental DNA strand and lighter one newly synthe­sized indicating semi conser­vative nature of DNA.
*Now in next generation when one strand heavier and one strand lighter bacteria divides it forms one bacteria with N15 strand and the other with N14 strand and the second bacteria produces both the strands of N14.
*This same process goes on like this, showing the Semi-C­ons­erv­ative nature of DNA.

Taylor's experiment on Vicia faba

Demons­trated the semico­nse­rvative method in the root tip of Vicia faba.
By Audior­adi­ogr­aphy.
Radioa­ctive thymidine used.
*The roots of Vicia faba were grown in medium containing radioa­ctive thymidine.
*In chromosome of 1st generation the radioa­ctive thymidine is found to be evenly distri­buted in both chromo­somes.
*In chromo­somes of 2nd generation only one of the two chromatids in each chromosome was radioa­ctive ie. 50% labelled.
*In 3rd generation only 25% was radioa­ctively labelled and so on, showing the semi conser­vative nature of DNA.
*As it is known that each chromatid is composed of only double helical of DNA, it is called replic­ation of DNA.