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Chapter 29: Problem 13

What is meant by the term molecular clock? How is this concept related to the neutral theory of evolution?

Short Answer

Expert verified
The term 'molecular clock' refers to the technique in molecular evolution that uses fossil constraints and rates of molecular change to deduce the time when life forms diverged. The neutral theory of evolution, which suggests that most evolutionary changes at a molecular level are due to the random drift of neutral mutants, is closely tied to this concept. It endorses the idea that if mutations are selectively neutral, they accrue at a constant rate over time in a given genetic element, much like a ticking clock.

Step by step solution

01

Understanding Molecular Clock

The molecular clock is a technique in molecular evolution that uses fossil constraints and rates of molecular change to deduce the time in prehistory when two or more life forms diverged. This implies that the time of such divergence can be calculated by observing the genetic mutations and their frequencies. The regular rate at which these mutations occur is referred to as the molecular clock.
02

Understanding Neutral Theory of Evolution

The neutral theory of evolution suggests that the majority of evolutionary changes at the molecular level are caused by random drift of selectively neutral mutants (not affecting survivability). It was proposed by Motoo Kimura in the late 1960s and it emphasizes the importance of genetic drift as opposed to natural selection in the evolutionary process.
03

Relating Molecular Clock to Neutral Theory of Evolution

The concept of molecular clock closely ties with the neutral theory of evolution. According to the theory, mutations accrue at a constant rate over time in a given genetic element when these mutations are all selectively neutral. This consistent change or 'ticking' is akin to a clock, hence the term 'molecular clock'. Therefore, the basic notion of the molecular clock hypothesis is a direct consequence of the neutral theory.

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Most popular questions from this chapter

Which would you expect to exhibit a faster rate of evolutionary change, the nucleotide sequence of a gene or the amino acid sequence of the encoded polypeptide of the same gene? Explain your answer.

If you were comparing the karyotypes of species that are closely related evolutionarily, what types of similarities and differences would you expect to find?

What is a species? What types of observations do researchers analyze when trying to identify species?

Would each of the following examples of reproductive isolation be considered a prezygotic or postzygotic mechanism? A. Horses and donkeys can interbreed to produce mules, but the mules are infertile. B. Three species of the orchid genus Dendrobium produce flowers 8 days, 9 days, and 11 days after a rainstorm. The flowers remain open for 1 day. C. Two species of fish release sperm and eggs into seawater at the same time, but the sperm of one species do not fertilize the eggs of the other species. D. Two tree frogs, Hyla chrysoscelis (diploid) and Hyla versicolor (tetraploid), can produce viable offspring, but the offspring are sterile.

When comparing the coding regions of a protein-encoding gene among closely related species, certain regions are commonly found to have evolved more rapidly (i.e., have tolerated more changes in sequence) than other regions. Explain why different regions of a protein-encoding gene evolve at different rates.
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