So, what about the molecular clock hypothesis? - …

Lepage T, Bryant D, Philippe H and Lartillot N (2007) A general comparison of relaxed molecular clock methods. Molecular Biology and Evolution 24: 2669–2680.

So, what about the molecular clock hypothesis

Tajima F (1993) Simple methods for testing molecular clock hypothesis. Genetics 135: 599–607.

PPT – Molecular Clock Hypothesis PowerPoint …

(The “Molecular Clock Hypothesis” means that all tips of the tree are equidistant from the root of the tree.) two log-likelihood values are calculated and displayed, one with and one without the clock hypothesis.

Molecular clock hypothesis - Revolvy

The molecular clock hypothesis originally rested on the assumption of rate constancy across lineages of a phylogeny, which would produce an approximately steady rate of accumulation of deoxyribonucleic acid or amino acid changes through time. This assumption has been questioned on the basis of increasingly large data sets, which have shown significant variability of rates in evolutionary lineages. To address this issue, tests have been developed to examine whether rates of molecular evolution vary significantly among taxonomic groups or phylogenetic lineages. Two major types of tests exist: those based on comparisons of genetic distances and those based on likelihood ratios. The first ones compare genetic distances between two species (or groups of species) relative to an outgroup; the latter ones compare maximum likelihood values for the same phylogeny calculated with and without the constant rate assumption. In those cases where the rate constancy assumption is violated, modern molecular clocks (relaxed clocks) are now being applied to implement the rate heterogeneity in the time estimation process.

Molecular clock tests have been developed to assess the validity of the rate constancy assumption for DNA and amino acid sequences.

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Takezaki N, Rzhetsky A and Nei M (1995) Phylogenetic test of the molecular clock and linearized tree. Molecular Biology and Evolution 12: 823–833.

The Molecular Clock Hypothesis: Biochemical Evolution, Genetic Differentiation and Systematics

Molecular Clock: Testing - eLS: Essential for Life Science

For the past 40 years, evolutionary biologists have been investigatingthe possibility that some evolutionary changes occur in a clock-likefashion. Over the course of millions of years, may build up in any given stretch of DNA at a reliable rate. For example,the gene that codes for the protein alpha-globin (a component of hemoglobin)experiences base changes at a rate of .56 changes per base pair perbillion years*. If this rate is reliable, the could be used as a molecular clock.

Molecular clocks. For the past 40 years, evolutionary biologists have been investigating the possibility that some evolutionary changes occur in a clock-like fashion.

Molecular Clock | Answers in Genesis

Battistuzzi FU, Filipski A, Hedges SB and Kumar S (2010) Performance of relaxed‐clock methods in estimating evolutionary divergence times and their credibility intervals. Molecular Biology and Evolution 27: 1289–1300.

Researchers such as Francisco Ayala have more fundamentally challenged the molecular clock hypothesis

Molecular clock - dnareplicationsystem - Google Sites

The original formulation of the molecular clock hypothesis refers to the approximately steady rate of accumulation of DNA or amino acid changes through time.