Biology · Molecular Basis of Inheritance · NEET
Taylor and colleagues used Vicia faba, the faba bean (also called broad bean). This is a plant, not a bacterium. Many students wrongly pick E. coli because Meselson and Stahl used E. coli. Remember: Meselson-Stahl = E. coli (bacterium); Taylor = Vicia faba (plant). For NEET, the option is almost always Vicia faba.
It proved that the DNA inside chromosomes also replicates semiconservatively. Meselson and Stahl had shown semiconservative replication for the DNA of a bacterium (E. coli). Taylor extended the same conclusion to the chromosomes of a higher organism (a plant). So the semiconservative model is true for chromosomes too, not just naked bacterial DNA.
He used radioactive (tritiated) thymidine. Thymidine is a building block of DNA, so any newly made DNA strand takes up the radioactive label. By tracking where the label goes into the daughter chromosomes, Taylor could see how the old and new DNA were distributed after replication.
Both proved semiconservative replication, but with different organisms and different labels. Meselson and Stahl used E. coli with a heavy nitrogen isotope (15N) and separated DNA by density on a CsCl gradient. Taylor used Vicia faba with radioactive thymidine and detected the label in chromosomes by autoradiography. Same conclusion, different method and material.
Taylor and colleagues performed the experiment in 1958, the same year Meselson and Stahl published their famous E. coli work. NCERT states 1958 clearly. A common NEET trick is to mix up the year or organism, so lock in: 1958, Vicia faba, radioactive thymidine, semiconservative chromosome replication.
Taylor conducted the experiments to prove semiconservative mode of chromosome replication on
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Vicia faba is a plant. It is the faba bean, also called the broad bean. Taylor chose it because its large chromosomes are easy to study under autoradiography.
No. Taylor used radioactive thymidine, a DNA base component. Heavy nitrogen (15N) was the label used by Meselson and Stahl in E. coli. Do not mix the two labels for NEET.
Taylor and colleagues in 1958 used radioactive thymidine on Vicia faba to prove that DNA in chromosomes also replicates semiconservatively. This exact line has appeared as a NEET question.
Meselson-Stahl proved semiconservative replication in bacterial DNA. Taylor showed the same rule holds inside real chromosomes of a higher (eukaryotic) organism. Together they make the semiconservative model universal.
