NEET BIOLOGY

Detailed explanation-1: -Viral Structure. In the simpler viruses the virion consists of a single molecule of nucleic acid surrounded by a protein coat, the capsid; the capsid and its enclosed nucleic acid together constitute the nucleocapsid. In some of the more complex viruses the capsid surrounds a protein core (Fig.

Detailed explanation-2: -The simplest virions consist of two basic components: nucleic acid (single-or double-stranded RNA or DNA) and a protein coat, the capsid, which functions as a shell to protect the viral genome from nucleases and which during infection attaches the virion to specific receptors exposed on the prospective host cell.

Detailed explanation-3: -A virus that has an outer wrapping or envelope. This envelope comes from the infected cell, or host, in a process called “budding off.” During the budding process, newly formed virus particles become “enveloped” or wrapped in an outer coat that is made from a small piece of the cell’s plasma membrane.

Detailed explanation-4: -Unlike cells (e.g. bacteria, plant and animal cells), viruses contain either DNA or RNA, never both; the viral nucleic acid is either single or double stranded. Viruses with a DNA core are capable of surviving in the nucleus of the cell they infect, using the host’s biochemical machinery to replicate their DNA.

Detailed explanation-5: -Viruses may also be classified according to the structure of the virus particle, or virion. The three major shapes seen are spherical, filamentous, and complex.