Question

Chimeric DNA is a
(A) DNA which contains uracil
(B) DNA synthesized from RNA
(C) Recombinant DNA
(D) DNA which contains single strand

Answer 1

Hint: DNA or deoxyribonucleic acid is helically twisted double stranded polymer of deoxyribonucleotides which is not only the largest macromolecule but also represents genetic material of organisms and molecular basis of heredity. DNA is an acidic substance. It was first isolated by Friedrich Meischer from the nucleus of a pus cell. He named it nuclein. In eukaryotes DNA is present inside the nucleus and mitochondria and plastids. Naked DNA i.e., DNA without histone association is present in prokaryotes. Since, nucleus is absent in prokaryotes , nuclear DNA is embedded in cytoplasm. It is called chromosomal DNA.

Complete answer:
Let’s discuss the given options.
(A) DNA which contains uracil: Prior to 1950, chemical components of DNA have been discovered. Chargaff’s rules and X-Ray crystallography helped in the derivation of DNA structure. In DNA, four types of deoxyribonucleotides occur. Deoxyribonucleotides consist of deoxyribose sugar, phosphoric acid and nitrogen base. Nitrogen bases are different in each deoxyribonucleotide. Two are 9-membered double ring purines, adenine and guanine. Other two are 6-membered sing ring pyrimidines, cytosine and thymine. Uracil is present in RNA in place of thymine.

(B) DNA synthesized from RNA: DNA synthesized from a single stranded RNA (messenger RNA or micro RNA) template in a reaction catalyzed by enzyme reverse transcriptase is called complementary DNA (cDNA). It is used to clone eukaryotic genes in prokaryotes.

(C) Recombinant DNA: The process of introduction of a foreign DNA into the genome which contains our gene of interest is called recombinant DNA technology and the DNA produced in such a way is called recombinant DNA. The technique is mainly used to change the phenotype of host organisms by introducing genetically altered vectors into the genome of the Organism. Recombinant DNA is also called Chimeric DNA.

(D) DNA which contains a single strand: A DNA molecule consisting of only a single strand instead of the typical two stranded nucleotides in helical form is called single stranded DNA. Found in Parvoviridae (class II Virus). They can also be produced artificially by rapidly cooling heat denatured DNA. Heat causes them to separate and rapid cooling prevents their renaturation.

So , the correct answer is option (C).

Note:
Recombinant DNA is created in a lab by the process of molecular cloning. A cloning vector is a DNA molecule that can self replicate inside a living cell. Methods involved in rDNA technology are: Choosing appropriate host organisms and cloning vectors. Preparation of vector DNA and DNA to be cloned. Creation of recombinant DNA. Introduction of recombinant DNA to host organisms. Screening of recombinant DNA with specific properties sought from host organisms.