Question

The first genetic material could be
A) Protein
B) Carbohydrates
C) DNA
D) RNA

Answer 1

Hint: The genetic material is the heredity substance that is present in the cell. It carries information specific to an organism from the parents to the offspring. The genetic material controls the organism's composition and it is usually identical in the somatic cells of multicellular organisms

Complete answer:
RNA was the first genetic material. Life processes have evolved around RNA. It used to act as genetic material as well as a catalyst but RNA being was reactive and unstable.

In prokaryotic cells whole of the RNA is found in the cytoplasm as there is no nucleus. In a eukaryotic cell bulk of the RNA occurs in the cytoplasm and a small amount of the nucleus, mitochondria and plastids. In the cytoplasm, it is mainly found in the ribosomes although some are present in the matrix. In the nucleus, with a small amount on the chromosome and some even in the nuclear sap.

The RNA molecule is a single chain of ribonucleotide units linked together by covalent bonds. Each ribonucleotide unit in turn consists of 3 different molecules: phosphate, ribose sugar and a nitrogenous base. In the RNA chain, the phosphate component at the 5' position of one ribonucleotide unit is joined by a phosphodiester bond to the sugar component of the next ribonucleotide unit at the 3' carbon atom. This forms a "backbone" of alternating sugar-phosphate - sugar components. The nitrogenous base molecules are joined to the sugar molecules at the 1' carbon attached by glycosidic bond and project on its one side.

The RNA molecule is normally a single strand. However, the strand may fold back upon itself, and the double-strand, thus formed, may get coiled giving RNA a pseudohelical structure. Base pairing in the pseudohelical regions is similar to that in DNA. In RNA, the purine and pyrimidines are not present in equal amounts, i.e. A +G is not equal to C+U, as in the case in DNA.

Therefore the correct answer is option ‘D’.

Note: The four nitrogen bases are A, U, C, G that are found in the RNA may occur in any sequence and the specific sequence may be repeated any number of times to form a complete molecule. This gives infinite variety to the RNA molecules.