Question

A segment of DNA contains 1200 nucleotides of which 200 have adenine base. How many cytosine bases are present in this segment of DNA?
a. 100
b. 200
c. 400
d. 800

Answer 1

Hint: As we know already, a molecule composed of two polynucleotide chains that coil around each other to form a double helix is called Deoxyribonucleic acid. This is present in our body which carries the genetic instructions for the development, functioning, growth, and reproduction of all recognized organisms and many viruses. The chemical compounds like DNA and ribonucleic acid (RNA) are said to be a nucleic acid.

Complete answer:
We know that the amount of hormone adenine released is equal to thymine released. In addition, the proportion of cytosine is equal to guanine since they are harmonizing bases bestowing to the Chargaff's rule.

It is said that there are about 200 adenine bases in the body. Thus, the number of thymine bases will be equal to adenine which is 200 bases. Where the total number of bases is 1200. Thus, the remaining bases are
\[1200 - (200 + 200) = \,800\]

Thus, we can say that among the 800 bases, the number of cytosine and guanine will be in similar proportions, which is equal to 400 bases each.

Hence, the correct answer is option (C).

Note: The DNA of any eukaryotic organism contains four chemical bases. Cytosine (C) is one of these four chemical bases in DNA. The other chemical bases are adenine (A), guanine (G), and thymine (T). The location of cytosine bases is on one strand that forms chemical bonds with guanine bases on the opposite strand within the DNA molecule. the cell's genetic instructions get encoded with the sequence of four DNA bases.