Question

RNA Genomes The RNA viruses have relatively small genomes. For example, the single-stranded RNAs of retroviruses have about 10,000 nucleotides, and the Q $\beta$ RNA is only 4,220 nucleotides long. Given the properties of reverse transcriptase and RNA replicase described in this chapter, can you suggest a reason for the small size of these viral genomes?

Name: Problem 9, Chapter 26: Principles of Biochemistry
Uploaded: 2021-10-13T11:02:21-08:00
Duration: 2 min 29 s
Channel: Rashmi Gondi
Description: RNA Genomes The RNA viruses have relatively small genomes. For example, the single-stranded RNAs of retroviruses have about 10,000 nucleotides, and the Q βRNA is only 4,220 nucleotides long. Given the properties of reverse transcriptase and RNA replicase described in this chapter, can you suggest a reason for the small size of these viral genomes?

   RNA Genomes The RNA viruses have relatively small genomes. For example, the single-stranded RNAs of retroviruses have about 10,000 nucleotides, and the Q $\beta$ RNA is only 4,220 nucleotides long. Given the properties of reverse transcriptase and RNA replicase described in this chapter, can you suggest a reason for the small size of these viral genomes?

Principles of Biochemistry

David L. Nelson,… 7th Edition

Chapter 26, Problem 9

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Solved by Expert Rashmi Gondi

10/13/2021

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This is because viruses do not need to encode the machinery to translate the genetic information. In other words, they do not need to carry as much genetic information as other organisms. Show more…

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RNA Genomes The RNA viruses have relatively small genomes. For example, the single-stranded RNAs of retroviruses have about 10,000 nucleotides, and the Q $\beta$ RNA is only 4,220 nucleotides long. Given the properties of reverse transcriptase and RNA replicase described in this chapter, can you suggest a reason for the small size of these viral genomes?

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Key Concepts

Error Threshold

Due to the high mutation rates introduced by error-prone replication enzymes, RNA viruses operate near an error threshold, beyond which the accumulation of deleterious mutations would compromise viability. This threshold effectively limits the maximum size of their genomes, favoring the evolution of smaller genomes that can be replicated with acceptable levels of genetic fidelity.

Replication Fidelity

RNA-dependent polymerases, such as reverse transcriptase and RNA replicase, generally lack proofreading activity. This low replication fidelity results in a high error rate during viral genome replication. As mutations accumulate quickly, maintaining a larger genome would lead to an unsustainable mutational burden, making high-fidelity replication mechanisms necessary for larger genomes, which these viruses lack.

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