Asked in PMC Practice Test 12 (2021) 2021Moderate

What is the approximate diameter of retroviruses?

Correct answer: B. 100 nm

  • A. 150 nm
  • B. 100 nm
  • C. 200 nm
  • D. 250 nm

Explanation

The virions are 80-100 nm in diameter, and their outer lipid envelope incorporates and displays the viral glycoproteins (Fig. 1). The shape and location of the internal protein core are characteristic for various genera of the family.

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About Viruses

Viruses are acellular infectious particles made of genetic material enclosed by a protein capsid, sometimes with a lipid envelope. Their replication depends on a host cell and may follow lytic or lysogenic cycles, so viral structure and reproduction differ fundamentally from those of cellular organisms such as bacteria.

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