正确

错误

不画人的眼仁

黑色幽默

改变事物的特质而进行创作

以上都不正确

Like retrotransposons, retroviruses use the enzyme reverse transcriptase to convert RNA into DN The enzyme is encoded by the retroviral genome, and a few molecules of the enzyme are packaged along with the RNA genome in each virus particle. When the single-stranded RNA genome of the retrovirus enters a cell, the reverse transcriptase brought in with it makes a complementary DNA strand to form a DNA/RNA hybrid double helix.

The RNA strand is removed, and the reverse transcriptase (which can use either DNA or RNA as a template) now synthesizes a complementary DNA strand to produce a DNA double helix. This DNA is then inserted, or integrated, into a randomly selected site in the host genome by a virally encoded integrase enzyme. In this integrated state, the virus is latent: each time the host cell divides, it passes on a copy of the integrated viral genome, which is known as a provirus, to its progeny cells.

The next step in the replication of a retrovirus—which can take place long after its integration into the host genome—is the copying of the integrated viral DNA into RNA by a host-cell RNA polymerase, which produces large numbers of single-stranded RNAs identical to the original infecting genome.

These viral RNAs are then translated by the host-cell ribosomes to produce the viral shell proteins, the envelope proteins, and reverse transcriptase—all of which are assembled with the RNA genome into new virus particles.

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错误

Most viral genes are expressed

The bacterial cell is lysed

Many new viruses are produced

Most normal bacterial functions are turned off.

The virus may become integrated into the host genome.

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