The Question Refers to the Following Table, Which Compares the Percent

question 71

Multiple Choice

The question refers to the following table, which compares the percent sequence homology of four different parts (two introns and two exons) of a gene that is found in five different eukaryotic species. Each part is numbered to indicate its distance from the promoter (for example, Intron I is the one closest to the promoter) . The data reported for species A were obtained by comparing DNA from one member of species A to another member of species A.
% Sequence Homology
$$\begin{array} { | l | l | l | l | l | } \hline \text { Species } & \text { Intron I } & \text { Exon I } & \text { Intron VI } & \text { Exon V } \\\hline \text { A } & 100 \% & 100 \% & 100 \% & 100 \% \\\hline \text { B } & 98 \% & 99 \% & 82 \% & 96 \% \\\hline \text { D } & 98 \% & 99 \% & 89 \% & 96 \% \\\hline \text { E } & 99 \% & 99 \% & 92 \% & 97 \% \\\hline\end{array}$$
Which of these four gene parts should allow the construction of the most accurate phylogenetic tree, assuming that this is the only part of the gene that has acted as a reliable molecular clock?

• A) Intron I
• B) Exon I
• C) Intron VI
• D) Exon V

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