Question

(a)How are the two strands of DNA helix held together?
(b)In chemical terms what are DNA and RNA?

Answer 1

Hint: The strands of the DNA helix are together by a weak bond. DNA and RNA are types of nucleic acids, i.e. made of nucleotides. DNA is an acidic substance present in the nucleus of the cell, mainly stores information. In the cytoplasm, they are associated with the synthesis of proteins.

Complete answer:
(a) The two strands of the DNA double helix are held together by a weak bond known as the hydrogen bonding. These bonds are formed between the complementary (opposite) base pairs of the DNA. There exist 3 hydrogen bonds between cytosine and guanine bases while 2 hydrogen bonds occur between the bases adenine and thymine of both the strands. Individually, these hydrogen bonds are weak but collectively they become quite strong.
(b)Deoxyribonucleic acid, usually, 2'-deoxy-5'-ribonucleic acid is the chemical term for DNA, and the RNA stands for ribonucleic acid.

Additional Information: -Nucleic acid was first discovered by Friedrich Miescher in the year 1869. He called the DNA as nuclein.
-The DNA was noticed in the chromosomes with the help of the Fuchsin staining technique developed by Feulgen in the year 1924.
-The DNA and RNA can be recognized based on pentose sugar and nitrogenous bases.
-The nitrogenous bases present in the DNA are of two types, Purines and Pyrimidines.
-James Watson and Francis Crick in the year 1953 proposed the double-helical structure of the DNA molecule.
-Ribose nucleic acid is a polymer of ribonucleotides that are made of a pentose ribose sugar, phosphoric acid, and nitrogenous bases (adenine, guanine, cytosine, and uracil).

Note: The DNA is usually made of 4 million nucleotides per cell and present in the chromosome and little is found in the mitochondria and chloroplasts. The RNA nucleotides are less in number, up to 12000 per cell, and are distributed throughout the cytoplasm of the cell except for the vacuoles.