Erwin Chargaff | Chargaff's rule | Experiment Performed By Chargaff

 Erwin Chargaff

Erwin Chargaff

In 1950, Erwin Chargaff did an experiment that gave his most famous rule that is Chargaff’s rule with his investigation.

Experiment.

• Chargaff isolates the DNA from the nuclei of the cell by the Salting out method.
• Then he identifies the DNA. 
• He breaks the DNA into pieces.
• He isolated the DNA from many organisms humans, bacteria, yeast, mice, etc.
• So he had mixtures of nitrogenous bases of DNA from many organisms.
• He separates the mixture of nitrogenous bases of DNA into purines and pyrimidines by paper chromatography.

Now, Why did Chargaff use paper chromatography for his experiment?

He used the paper chromatography technique for the experiment to separate the mixtures of nitrogenous bases from the mixture. Because in paper chromatography different substances travel different distances when they are exposed to solvent.

• He exposed the purines and pyrimidines to ultraviolet light. 
• He used ultraviolet light in his experiment to visualize the separation of purines and pyrimidines on the chromatograph paper.

Conclusion.

The number of purines and pyrimidines is equal.

Now, what are purines and pyrimidines?

Two nitrogenous bases adenine and guanine form hydrogen between themselves. This structure is called purines. While the nitrogenous bases cytosine, thymine, and uracil also form hydrogen bonds and are called pyrimidines.

In the case of DNA, the pyrimidines have cytosine and thymine because uracil is not part of DNA.

• Adenine binds with thymine and guanine binds with cytosine in DNA.
• The amount of guanine is equal to the amount of cytosine, and the amount of adenine is equal to the amount of thymine in every organism.

Chargaff's rule