Question

If DNA of a particular species was analyzed and it was found that it contains 27 percent A, what would be the percentage of C?

a. 27 percent

b. 30 percent

c. 23 percent

d. 54 percent

Short answer

According to Chargaff's law of DNA base equivalency, the percentage of adenine in a species' DNA is $27$ and the percentage of cytosine in the species' DNA is$23$.

Step-by-step solution

Step:1 Introduction

Except for a few viruses, deoxyribonucleic acid (DNA) is the genetic substance of all living things. Watson and Crick presented the double helix model to describe the structure. It is made up of two strands of polynucleotides. A nucleotide is made up of a nitrogenous base, a sugar called deoxyribose, and phosphoric acid. Purines are nitrogenous bases that contain adenine(A) and guanine(G), while pyrimidines include cytosine(C) and thymine (T).

Step:2 Correct answer

Option (c) has a percentage of 23 percent. The percentage of cytosine in a species' DNA is 23 if the amount of adenine in the DNA is 27. As a result, Option (c) is right.

Step:3 Explanation of the solution

The ratio of purines and pyrimidines in the DNA of cells in an organism is 1:1, according to Chargaff's law of base equivalency. The amounts of adenine and thymine are the same, and the amounts of guanine and cytosine are the same. As a result, their percentages are likewise the same. It is assumed that the adenine content is $27$percent. As a result, the guanine content is also $27$percent.

If the ratio of cytosine to thymine is $46$, the ratio of cytosine to thymine is$23$.

Step:4 Explanation for the incorrect answer

Option (a) is provided as $27$percent. Adenine has a percentage of $27$and guanine has a percentage of $27$. So, it is an inaccurate answer.

Option (b) is offered as $30$percent. It has nothing to do with the percentage of nitrogenous nucleotides in the cell's DNA. As a result, it is an inaccurate response.

Option (d) receives $54$percent of the vote. It is the sum of the percentages of adenine and guanine. As a result, it is an inaccurate response.

As a result, choices (a), (b), and (d) are erroneous.