Question

Answer the following question in your own words.

Describe the structure of the DNA molecule.

Answer 1

1. All organisms have the same DNA structure. Watson and Crick modelled DNA in 1953. In this model, two parallel nucleotide threads coil around each other. A ‘double helix’ describes this arrangement. Like a coiled ladder, its construction is flexible.
2. The DNA strands include many tiny ‘nucleotide’ molecules. Four nitrogenous bases are adenine, guanine, cytosine, and thymine. Cytosine and thymine are pyrimidines and adenine and guanine are purines.
3. A nitrogenous base, phosphoric acid, and sugar molecule form the nucleotide.
4. Four types of nitrogenous bases equal four types of nucleotides.
5. DNA has a chain of nucleotides. Each ladder rail is constructed of alternately connected sugar and phosphoric acid molecules, like the DNA molecule's two threads. Every ladder step is two nitrogenous bases connected by hydrogen bonds. Adenine always connects with thymine, cytosine with guanine.

                                      Structure of DNA

DNA (Watson and Crick’s Model)