NEET BIOLOGY

Detailed explanation-1: -Viruses are smaller and simpler in construction than unicellular microorganisms, and they contain only one type of nucleic acid-either DNA or RNA-never both.

Detailed explanation-2: -These require the host cellular machinery to replicate and propagate their infection. The genetic material in viruses is either RNA or DNA. It is not possible for a virus to contain both RNA and DNA. This is because (biologically speaking), there doesn’t seem to be any need for it.

Detailed explanation-3: -Viruses are microscopic parasites responsible for a host of familiar – and often fatal – diseases, including … the flu, Ebola, measles and HIV. They are made up of DNA or RNA encapsulated in a protein shell and can only survive and replicate inside a living host, which could be any organism on earth.

Detailed explanation-4: -Viral genomes consist of DNA or RNA only, never both. DNA and RNA molecules can be double stranded or single stranded, linear or circular (Fig. 1.6), segmented (composed of multiple pieces of nucleic acid) or nonsegmented.

Detailed explanation-5: -Microscopes proved the existence of single-celledbacteria. However, there was debate about whether bacteria had genes and what attributes they may have in common with higher life forms.