42. A molecular clock is best defined as a. the information contained in DNA or protein...

42. A molecular clock is best defined as

a. the information contained in DNA or protein sequences that shows changes over time.

b. genes that under selective pressure show a higher rate in mutation frequencies.

c. organisms in favorable environments that have greater offspring potential.

d. the time between Earth’s formation and the beginnings of life in an RNA world.

e. a monophyletic group of organisms that replicate in synchrony.

Expert Solution

The correct answer is option a). stating that the information contained in DNA or protein sequences that show changes over time.

To study the molecular basis of evolution, molecular clock technique is being used since 1962. In this techniques biomolecules (generally DNA & their nucleotide sequences and Proteins and their amino acid sequences) are used as biomolecular data to study mutation (change in their sequence) to know the time in pre-history when they diverged. The study of DNA and protein sequence changes over time is the basis of Neutral theory of molecular evolution given by Motoo Kimura.

Option b is incorrect: The statement defines that under selective pressure genes show higher mutation frequecies, but rather opposite. Genes under selection preseeure are important because these genes are necessaryt for survival of organisms. Hence, such genes show high degree of conservation. Hence. this can not be a correct answer

Option c is incorrect: This statement is talking about fitness of an organism in certain envioronment due to their high fecundity and it is not relevant to molecular clock.

Option d is incorrect: This statement better defined as RNA world Hypothesis. This hypothesis suggests that RNA with selp replicating capacity started the life. (Discovery of Ribozyme gave some credence to this theory)This statement is no way related to molecular clock

Option e is incorrect: The statement " a monophyletic group of organisms that replicate in synchrony " also does not explain molecular evolution based on DNA or protein sequence change over time hence this option is also incorrect.

gladiator answered 2 years ago

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