If a double-stranded segment of DNA has been found to have 23 purines and 15 thymines, how many guanines are there?

Explanation: Following Chargaff's ratio that describes the ration of purines to pyrimidines as 1:1, if there are 23 purines, it follows that there should be 23 pyrimidines; 15 Thymines should therefore be hydrogen bonded to 15 Adenines by complementary base pairing.

We are then left with 8 nucleotides composed of guanines and cytosines in complementary base pairs. This means that half that number (4) should be guanines and the rest cytosines.

kasliwalalvi24 kasliwalalvi24 · Answer 2 · 2021-12-07T11:34:14+01:00

The DNA is a double-stranded molecule, which is made up of purine, pyrimidine, a pentose sugar, and phosphate backbone. Chargaff's rule states that any species will have a stoichiometric ratio of 1:1.

The number of guanines in the double-stranded DNA is 4.

In the DNA, the base pairing occurs as:

The guanines bind with cytosine through hydrogen bonding. The adenine binds with thymine with two hydrogen bonds.

In the given nucleotide, there are 23 purines (guanine and adenine). There are 15 thymines in the DNA molecule.

Based on the Chargaff rule, the 15 thymines will bind to adenine, leaving only 4 guanines and 4 cytosines. Thus, there will be 4 cytosines left to bond with the guanines to achieve Chargaff's ratio of 1:1.

Therefore, the guanine in the nucleotides will be 4.

To know more about Chargaff's rule, refer to the following link:

https://brainly.com/question/19156457