Question

The backbone of DNA is made up of?
(a) Sugar only
(b) Lipid and phosphate
(c) Protein and phosphate
(d) Sugar and phosphate

Answer 1

Hint:The full form of DNA is Deoxyribonucleic Acid. DNA is a set of molecules responsible for transmitting and carrying the inherited materials or genetic instructions from parents to children. It is an organic chemical molecule found in all prokaryotic and eukaryotic cells.

Complete answer:
DNA is made up of nucleotide molecules. Every molecule of nucleotide contains one phosphate group, one sugar group, and one nitrogen base. The backbone of the DNA is composed of deoxyribose sugar and a phosphate molecule.
The four types of nitrogen bases present in a nucleotide are adenine (A), thymine (T), guanine (G), and cytosine (C). The order of these bases determines the DNA's instructions or genetic code.
The nucleotides are attached to each other to form two long strands of DNA that spiral with each other to create a structure called a double helix. So, DNA is said to be the double-helical structure.
If we think of the double helix structure of DNA as a ladder, the phosphate and sugar molecules would be the sides of the ladder, whereas the bases would be the rungs of the ladder.
The bases on one strand pair with the bases on another strand meaning adenine on one strand pairs with the thymine of another strand, and similarly the guanine of one strand pairs with the cytosine of the opposite strand.
The bond between adenine and thymine may be a hydrogen covalent bond whereas the bond between guanine and cytosine is that hydrogen triple bond.
The DNA molecules are quite long so that they can not fit into cells without the proper packaging. To fit inside cells, DNA is coiled tightly to make structures called chromosomes.

So, the correct answer is ‘Sugar and phosphate’.

Note:
In 1953 Watson and Crick proposed the double helix structure of DNA 1953. Nikolai Koltsov was the first to anticipate the semiconservative model of the DNA and this model was later by Meselson-Stahl in their experiment. They conducted an experiment to confirm that the DNA replicated through semi-conservative means with the help of two radioisotopes: nitrogen-15 (15N) and nitrogen-14 (14N).