Question

The part of the DNA molecule that varies among DNA molecule is
A. Phosphate molecule
B. Nitrogen base
C. Sugar molecule
D. All of the above

Answer 1

Hint: DNA is a long polymer of deoxyribonucleotides. It is a molecule composed of polynucleotide chains that coil around each other to form a double helix. The length of DNA is defined as the number of nucleotides. DNA carries the genetic information of an organism. It is a hereditary molecule. DNA is responsible for carrying genetic information to form parents to progeny.

Step by step answer:The nucleic acids DNA and RNA are the polymers of nucleic acids. These are composed of a nitrogenous base, a pentose sugar, and a phosphate group.
Option -A- Phosphate molecule
The phosphate group in DNA does not change. This phosphate group of one nucleotide binds covalently with a sugar molecule of the next nucleotide. It forms a long polymer of nucleotide monomers. These sugar-phosphate groups constitute the backbone of each strand of a DNA molecule. The phosphate group remains the same for each DNA molecule.
Option -B-Nitrogen base
The DNA molecules vary because of the nitrogenous bases i.e. purines and pyrimidines. These combine according to Chargaff's rule i.e. complementary base pairing occurs in them. Purines are Adenine and Guanine while pyrimidine is Cytosine and Thymine in DNA. These bases are joined by hydrogen bonds in DNA. Adenine combines with Thymine of the opposite strand with two hydrogen bonds and Guanine combines with Cytosine with three hydrogen bonds. So according to this base-pairing, there are differences in DNA molecules.
Option -C- Sugar molecule
In DNA the sugar molecule present in each DNA molecule is pentose sugar i.e. deoxyribose sugar. This is the only sugar molecule present in the DNA and it does not vary within DNA.
So, the correct answer to this question is an option” B” Nitrogen base.

Note: In DNA the two polynucleotide chains have anti-parallel polarity based on base pairing in the double helix of the DNA. These two chains are coiled in a right hand-fashioned.