Related Experiment Video
Updated: Jul 26, 2026
08:14
Kinetics of Lagging-strand DNA Synthesis In Vitro by the Bacteriophage T7 Replication Proteins
Published on: February 25, 2017
Kinetics of rapid RNA evolution in vitro
1Research Foundation of Southern California, Inc., La Jolla 92037.
Journal of Molecular Evolution
|October 1, 1991
Summary
Researchers observed that Q beta RNA variants rapidly developed partial resistance to ethidium bromide (EB). This resistance arose from pre-existing mutant RNA molecules, demonstrating natural selection principles in RNA evolution.
Area of Science:
- Molecular Biology
- Evolutionary Biology
- Virology
Background:
- Spiegelman and coresearchers previously observed rapid partial resistance to ethidium bromide (EB) in Q beta RNA variants during in vitro replication.
- This phenomenon suggested the presence of a pre-adapted mutant RNA pool within the replicating population.
Purpose of the Study:
- To quantitatively analyze the replication kinetics of midivariant RNA to understand the mechanisms of rapid ethidium bromide resistance.
- To investigate the evolutionary dynamics, including cross-propagation and selection pressures, in RNA variant populations.
Main Methods:
- Quantitative analysis of RNA replication kinetics under defined in vitro conditions.
- Competitive replication assays involving Q beta RNA variants and ethidium bromide.
- Characterization of mutant RNA pools and their propagation dynamics.
Main Results:
- A pool of pre-adapted mutant RNA molecules was identified, capable of cross-propagation from optimal species like MDV-1.
- The evolution exhibited DNA-like features, including adherence to the fundamental theorem of natural selection.
- Suppression of intrinsic RNA heterogeneity through sampling and detection methods, alongside the dominance of self-propagation, influenced variant ascendancy.
Conclusions:
- Rapidly acquired resistance to ethidium bromide in RNA variants is driven by pre-existing, pre-adapted mutants.
- RNA evolution in this context mirrors DNA evolution, adhering to natural selection principles.
- Understanding these dynamics is crucial for considering strategies against viral drug resistance.
Related Concept Videos
00:36Viral Mutations
A mutation is a change in the sequence of bases of DNA or RNA in a genome. Some mutations occur during replication of the genome due to errors made by the polymerase enzymes that replicate DNA or RNA. Unlike DNA polymerase, RNA polymerase is prone to errors because it is not capable of “proofreading” its work. Viruses with RNA-based genomes, like HIV, therefore accrue mutations faster than viruses with DNA-based genomes. Because mutation and recombination provide the raw material for adaptive...
01:53RNA Stability
Intact DNA strands can be found in fossils, while scientists sometimes struggle to keep RNA intact under laboratory conditions. The structural variations between RNA and DNA underlie the differences in their stability and longevity. Because DNA is double-stranded, it is inherently more stable. The single-stranded structure of RNA is less stable but also more flexible and can form weak internal bonds. Additionally, most RNAs in the cell are relatively short, while DNA can be up to 250 million...
02:05Gene Evolution - Fast or Slow?
The genomes of eukaryotes are punctuated by long stretches of sequence which do not code for proteins or RNAs. Although some of these regions do contain crucial regulatory sequences, the vast majority of this DNA serves no known function. Typically, these regions of the genome are the ones in which the fastest change, in evolutionary terms, is observed, because there is typically little to no selection pressure acting on these regions to preserve their sequences.
In contrast, regions which code...
In contrast, regions which code...
01:53RNA Stability
Intact DNA strands can be found in fossils, while scientists sometimes struggle to keep RNA intact under laboratory conditions. The structural variations between RNA and DNA underlie the differences in their stability and longevity. Because DNA is double-stranded, it is inherently more stable. The single-stranded structure of RNA is less stable but also more flexible and can form weak internal bonds. Additionally, most RNAs in the cell are relatively short, while DNA can be up to 250 million...
00:43Bacterial RNA Polymerase
Unlike eukaryotes, bacteria use a single RNA Polymerase (RNAP) to transcribe all genes. The different subunits of bacterial RNAPhave distinct functions. The multisubunit structure of the bacterial RNAP helps the enzyme to maintain catalytic function, facilitate assembly, interact with DNA and RNA, and self-regulate its activity.
In most genes, the transcription site is a single base present upstream of the coding sequence. Though RNAP is a catalytically efficient enzyme, it does not recognize...
In most genes, the transcription site is a single base present upstream of the coding sequence. Though RNAP is a catalytically efficient enzyme, it does not recognize...
01:53Bacterial Transcription
RNA polymerase (RNAP) carries out DNA-dependent RNA synthesis in both bacteria and eukaryotes. Bacteria do not have a membrane-bound nucleus. So, transcription and translation occur simultaneously, on the same DNA template.
Transcription can be divided into three main stages, each involving distinct DNA sequences to guide the polymerase. These are:
Transcription can be divided into three main stages, each involving distinct DNA sequences to guide the polymerase. These are: