Question

Coliphage $\phi \times 174$ virus contains-
a. Single-stranded RNA
b. Double-stranded RNA
c. Single-stranded DNA
d. Double-stranded DNA

Answer 1

Viruses are non-cellular, microscopic infectious agents. They can only replicate inside a host cell. Viruses cannot be classified as either they are a living organism or non-living. $\phi \times 174$ is a virus that infects the bacteria E. coli. Hence $\phi \times 174$ is a bacteriophage.

Complete answer:
The $\phi \times 174$ bacteriophage is a single-stranded DNA virus that infects E. coli. This sequence work was completed in 1977 by Fred Sanger and his team. A protein coat that envelopes a core that contains both protein and DNA, each complete infectious particle of $\phi \times 174$.

This bacteriophage has a circular ss DNA genome which is made up of 5386 nucleotides.
$\pi \times 174$ encodes 11 genes. Out of these 11 genes, essential to viral morphogenesis are only 8 genes. The beginning of the infection is marked when G protein binds to lipopolysaccharides on the bacterial host cell surface.

The minus strands of these DNA molecules serve as templates for the synthesis of mRNA and some complementary (+) strands of DNA, each of which will later be packaged into the core of a new virion.

Hence, the correct answer is option (C).

Additional information:
PMVs are enveloped with ssRNA viruses. Double-stranded RNA has been found as the genetic material of many plants, animal, fungal, and bacterial viruses.
Most double-stranded DNA viruses replicate within the nucleus of the host cell. Some of the examples are polyomaviruses, adenoviruses, and herpesviruses-poxviruses, however, replicate in the cytoplasm.

Note: The DNA molecule is single-stranded and is in the form of a closed circle. It contains 5386 nucleotides. This tiny genome was the first DNA genome ever to be sequenced in 1977 by Fred Sanger. Its ssDNA molecule is inserted into the cell when $\phi \times 174$ attaches to its host. Here the DNA strand (+) serves as the template for the synthesis of a complementary (−) strand.