DNA is a macromolecule. How are nucleotides arranged in DNA?
1 Answer
DNA is a large molecule in living organisms that carries information for the functioning and reproduction of the cell.
Explanation:
DNA or Deoxyribonucleic acid is a macromolecule with a special composition and unique properties that sets the living apart from the non-living.
DNA is a nucleic acid which along with proteins, carbohydrates and lipids make up the chemical composition of most life forms. RNA is another nucleic acid.
DNA is most often a set of two long stands (each strand a polynucleotide) twined together as a double helix. Each polynucleotide (= many nucleotides) strand is made of series of monomer (= single unit) nucleotides .
The paired strands of DNA face each other, as nucleotides of two strands form pairs by hydrogen bonds. These two strands when read from 5' to 3' end, are anti-parallel.
Each nucleotide is composed of :
- one of four nitrogen-containing nucleobases — cytosine (C), guanine (G), adenine (A), or thymine (T)
- a 5carbon sugar called deoxyribose, and
- a phosphate group.
The nucleotides of one strand are joined to one another in a chain by diester bonds between the sugar of one nucleotide (3') and the phosphate of the next (5'), resulting in a sugar-phosphate backbone .
The DNA backbone is resistant to cleavage.
In a double stranded DNA, A always pairs with T while G always pairs with C. This is why the two antiparallel strands are complementary and both strands of the double-stranded structure store the same biological information. This information is replicated as and when the two strands separate.
In prokaryotic cell, single circular DNA acts as genetic material. In eukaryotic cell linear DNA molecules are present, associated with histone proteins, forming chromosomes.
