Introduction to Viruses

Which of the following statements about viruses is true?

• Viruses are infectious particles that must use a "host" cell to produce new viruses

• Viruses are considered living things because they reproduce

• Viruses contain DNA, RNA, or both nucleic acids surrounded by a capsid, or protein coat

• There are many different types of viruses. However, they can be very well recognized due to their singular shape and structure.

Scientists estimate that at this time there are approximately 10³¹ viruses present on Earth.

• True

• False

Even though there are many viruses of different shapes and structures, most are found in oceans, where they attack bacteria and other microbes.

• True

• False

Which of the following statements about viruses is not true?

• They are microscopic, infectious particles that can reproduce only by infecting a host cell.

• They use the host cell and its resources to make more viruses, or the host cell becomes a virus factory

• Because viruses can't reproduce on their own, they are considered nonliving

• Viruses are made of microscopic cells that are composed of protein and nucleic acid

Which of the following statements is not true?

• Viruses, though very different, have some important features in common with cell-based life.

• Viruses have nucleic genomes based on the same genetic code that are used by your cells

• Viruses have genetic variation and can evolve

• Viruses are living particles that infect living cells

Which of the following statements is not true?

• Even though bacteria and viruses are very different, they both can be controlled by antibiotics

• Viruses are much smaller than bacteria

• Though bacteria are small and single-celled, they do not depend upon a host cell to reproduce

• Bacterial and viral infections are treated differently

Which of the following statements is not true?

• Viruses differ in shape, size, and life cycles

• The protective shell, or protein coat, is called a capsid

• Viruses contain nucleic acid within the capsid, of which can be either DNA, RNA, or both

• Many viruses have an outside layer called an envelope, which helps viruses avoid the host cells immune system

• Glycoproteins on the surface of the envelope help to identify and bind to receptor sites on the host's membrane

The protein coat, or capsid, is encoded within the viral genone of each virus, and therefore the virus contains the information for the structure of the capsid and not the host cell. Which of the following if a type of viral capsid?

• icosahedral

• filamentous

• head-tail

• icosahedral, filamentous, head-tail

The instructions for the structure of the viral envelope comes from the viral genome.

• True

• False

Although envelopes are common, especially among animal viruses, they are not found in every virus.

• True

• False