Question

What is DNA?

Answer 1

DNA is present inside the nucleus of a cell which consists of a nitrogen base, phosphate group and ribose sugar. It helps in replication make copies of DNA and also helps in the transcription process to make copies of DNA.

Complete answer:
DNA is a nucleic acid made up of acidic substances and helically twisted in the form of a double chain. It is made up of a nitrogen base, ribose sugar and a phosphate group. It is the largest macromolecules and also a genetic material of living organisms which helps the transfer of genetic material from one generation to the next generation.
In eukaryotes, DNA was present inside the nucleus, mitochondria and chloroplasts whereas in prokaryotes DNA is present in free form which is known as nuclear DNA. The DNA inside the nucleus forms histone protein to form chromatin fibres whereas DNA inside the mitochondria and chloroplast does not form histone protein. In DNA purine and pyrimidine occurs in the same amount, the purine of DNA are adenine and guanine whereas the pyrimidine is thymine and cytosine. Adenine has the same ratio as that of thymine whereas guanine has the same ratio as that of cytosine and the base ratio of these nitrogen bases does not change with the age and tissues, it remains the same in all species.

Note:
DNA was first isolated by Friedrich Meischer and called Nuclein and it was first isolated in the nucleus of pus cells. The chemical composition of DNA was discovered by E.E Chargaff and the derivation of the DNA structure rule was named Chargaff's rule.