molecular clock


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molecular clock

n.
1. An assumed approximately constant rate of change over evolutionary time in the nucleotide sequences of DNA molecules and the amino acid sequences of protein molecules.
2. A technique based on this assumption, in which the amount of time since two species or other taxa diverged from a common ancestor is estimated by measuring the number of differences between certain gene or protein sequences of the taxa.
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A molecular clock dates the common ancestor of European-type porcine reproductive and respiratory syndrome virus at more than 10 years before emergence of disease.
Results of the likelihood ratio tests for a molecular clock indicated that Peruvian YFVs in different subclades are evolving at different rates; trees constructed under the null model, allowing for rate heterogeneity, were assigned a statistically higher likelihood score than trees reconstructed with the molecular clock enforced.
Erwin, a paleontologist at the Smithsonian Institution's National Museum of Natural History in Washington, D.C., says the new study improves on past molecular clock efforts.
But recent findings threaten to underminethe neutrality theory--at least for some applications--and leave the molecular clock on a thin theoretical foundation.
Hence, the molecular clock can physiologically drive innate immune cell recruitment and the outcomes of asthma in humans, or airway inflammation in mice -- the review notes.
In recent years, scientists seeking to unlock the mysteries of our species' evolution have used DNA analyses to provide a "molecular clock" to date fossils, based on assumptions about the rate of genetic change per generation.
"Every single cell in our body has its own molecular clock, including all the machinery required for the body to know what time it is," says Gaudet.
This continuous reduction of telomere length functions as a "molecular clock" that counts down to the end of cell growth.
The new study, published in the journal Proceedings of the National Academy of Sciences, used "molecular clock" techniques to provide a more accurate record.
Molecular clock and phylogenetic analysis of seven ZIKV sequences from patients in Brazil suggest a single introduction into Brazil between May and December 2013, coinciding with increased air travel from ZIKV endemic areas and outbreaks in the Pacific Ocean [23].
Kusunose et al., "The intrinsic microglial molecular clock controls synaptic strength via the circadian expression of cathepsin S," Scientific Reports, vol.
We estimated the time of most recent common ancestor for all gene segments by using a relaxed molecular clock (Table).

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