The RNA virus in Figure 19.8 has a viral RNA polymerase that functions in step 3 of the virus’s replicative cycle. Compare this with a cellular RNA polymerase in terms of the template and overall function. (see Figure 17.10)

Short Answer

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The viral RNA polymerase and the cellular RNA polymerase are involved in synthesizing complementary RNA molecules to a template strand. However, viral RNA polymerase uses RNA of the viral genome as a template to synthesize mRNA.

On the other hand, cellular RNA polymerase uses one of the DNA strands as a template to synthesize mRNA molecules.

Step by step solution

01

Role of viral RNA polymerase in the replicative cycle

When an RNA virus binds to the receptor molecules of the host cell, it releases its viral genome into the cell. When the genome enters the cell, the replicative cycle of the virus is initiated.

The viral RNA polymerase uses the single-stranded RNA genome of the virus as a template to synthesize complementary RNA molecules. These complementary RNA molecules are then used to make new copies of the viral genome.

02

Role of cellular RNA polymerase in transcription

Transcription is when genetic information in the DNA molecule is decoded to form an mRNA molecule. During this process, cellular RNA polymerase binds to the promoter region of the template DNA strand.

RNA polymerase then uses the DNA strand as a template to synthesize mRNA molecules by adding RNA nucleotides to the 3’end of the growing RNA strand.

03

Comparison of viral RNA polymerase and cellular RNA polymerase

Viral RNA polymerase uses single-stranded RNA of the virus as a template to synthesize mRNA molecules, while cellular RNA polymerase uses DNA as a template to synthesize mRNA molecules.

Viral RNA polymerase synthesizes mRNA molecules to make new copies of the viral genome, whereas cellular RNA polymerase synthesizes mRNA from DNA to synthesize proteins in the cells.

Thus, both the RNA polymerases are involved in the synthesis of complementary mRNA molecules.

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Most popular questions from this chapter

RNA viruses require their own supply of certain enzymes because

(A) host cells rapidly destroy the viruses.

(B) host cells lack enzymes that can replicate the viral genome.

(C) these enzymes translate viral mRNA into proteins.

(D) these enzymes penetrate host cell membranes.

The phylogenetic tree shows the hypothesized evolutionary relationship between the variant strains of the H1N1 virus. The more closely connected the two variants are, the more alike they are in terms of HA gene sequence. Each fork in a branch, called a node, shows where two lineages separate due to different accumulated mutations. The length of the branches is a measure of how many sequence differences there are between the variants, indicating how distantly related they are. Referring to the phylogenetic tree, which variants are more closely related to each other: A/Taiwan/1018/2011 and A/Taiwan/552/2011 or A/Taiwan/1018/2011 and A/Taiwan/8542/2009? Explain your answer.

The scientists arranged the branches into groups made up of one ancestral variant and all of its descendants, mutated variants. They are color-coded in the figure. Using group 11 as an example, trace the lineage of its variants. (a) Do all of the nodes have the same number of branches or branch tips? (b) Are all of the branches in the group the same length? (c) What do these results indicate?

When bacteria infect an animal, the number of bacteria in the body increases in an exponential fashion (graph A). After infection by a virulent animal virus with a lytic replicative cycle, there is no evidence of infection for a while. Then the number of viruses rises suddenly and subsequently increases in a series of steps (graph B). Explain the difference in the curves.

The graph at the lower left shows the number of isolates collected (each from an ill patient) on the y-axis and the month and year that the isolates were collected on the x-axis. Each group of variants is plotted separately with a line color that matches the tree diagram. (a) Which group of variants was the earliest to cause the first wave of H1N1 flu in over 100 patients in Taiwan? (b) After a group of variants had a peak number of infections, did members of that same group cause another (later) wave of infection? (c) One variant in group 1 (green, upper-most branch) was used to make a vaccine that was distributed very early in the pandemic. Based on the graphed data, does it look like the vaccine was effective?

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