NEET BIOLOGY

Detailed explanation-1: -The amount of adenine is always equal to the amount of thymine found in a sample. The amount of cytosine is always equal to the amount of guanine found in a sample. The proportion of the four nitrogenous bases varies from species to species.

Detailed explanation-2: -Between 1885 and 1901, Kossel discovered that these acids were composed of five nitrogen bases: adenine, cytosine, guanine, thymine, and uracil.

Detailed explanation-3: -Chargaff’s rules state that in the DNA of any species and any organism, the amount of guanine should be equal to the amount of cytosine and the amount of adenine should be equal to the amount of thymine. Further a 1:1 stoichiometric ratio of purine and pyrimidine bases (i.e., A+G=T+C ) should exist.

Detailed explanation-4: -The DNA molecule is made up of very long chains of the 4 bases: A, C, G and T. In 1950, Erwin Chargaff published a paper stating that in DNA of any given species, the ratio of adenine to thymine is equal, as is the ratio of cytosine to guanine.

Detailed explanation-5: -To test the idea that DNA might be a primary constituent of the gene, Chargaff performed a series of experiments. He fractionated out nuclei from cells. He then isolated the DNA from the nuclei and broke it down into its constituent nucleic acids.