Question

How do nucleotides form DNA?

Answer 1

Hint: The nucleotides are the building block of nucleic acids and consist of a sugar molecule, phosphate group, and nitrogenous bases. They polymerize to form polynucleotides.

Complete answer:
DNA is a molecule that contains the genetic code of an organism. It is responsible for bringing out the genetic variation in human beings. The basic structural unit of the DNA is called the nucleosome. They are the repeating unit in the eukaryotic chromatin and give the appearance of beads on a string. A single nucleosome has around 150 base pairs of DNA.

DNA is a double helical structure formed by two polynucleotide chains that are complementary and run anti-parallel to each other. These two nucleotide chains are the polymers of nucleotides. A nucleotide is a structural unit of DNA that is made up of- a sugar molecule (deoxyribose), a phosphate group, and nitrogenous bases. Adenine and guanine are the two purine nitrogenous bases, and cytosine and thymine are the two pyrimidine nitrogenous bases found in the DNA. These nitrogenous bases determine the DNA sequence of our body.

Each strand of the DNA molecule is formed by the monomer units- nucleotides. The backbone of the chain is formed by the sugar molecules and the phosphate group. The two strands of the DNA molecule are held together by the nitrogenous bases. The purine bases pair up with the pyrimidine bases through hydrogen bonds. Adenine binds with thymine through two hydrogen bonds, while cytosine binds with guanine through three hydrogen bonds. These nitrogenous bases also provide complementarity in the DNA chain and are present at right angles to the chain.
The double helix structure of DNA was given by- James Watson and Francis Crick.

Note: The DNA forms the double helix structure by wounding two strands of DNA molecules in an antiparallel manner. The helix is right winded and has 10-10.5 pairs of bases in its every turn. The long-stranded DNA molecules are twisted, condensed, and packed to form chromosomes in a cell.