Full Question:
Before the three-dimensional structure of DNA was discovered, scientists knew that DNA contained nitrogenous bases. The table below shows the percentages of the nitrogenous bases in a DNA sample. Which rule can be used to determine the percentages of the missing nitrogenous bases? Complete the table AND explain your answer.
Base Percent Adenine 23 Thymine ___ Cytosine 27 Guanine ____
Answer:
Chargaaf's rule can be used to find out missing percentages. Thymine will be 23% and Guanine will be 27%.
Explanation:
Chargaaf was a very popular scientist who worked on the DNA even before Watson and Creek discovered the DNA structure. Its even very evident that because of Chargaaf's rules, Watson and Creek were able to formulate their structure of DNA.
One of the rules of Chargaaf said that the ratio of purines to pyrimidines in a DNA is always 1:1. That means the summation of adenine and guanine is to thymine and cytosine will be 1:1. This is actually because adenine is complementary to thymine and guanine to cytosine.
Thus in the given DNA chart, adenine is 23%. So, thymine will also be 23%. Its given that cytosine is 27%. So, guanine will also be 27%. The answer can be checked as the summation of all the numbers give a total of 100%.
