Phylogeny

AP Biology· difficulty 4/5

A short unknown DNA sequence is BLASTed and the top hit is a sea urchin gene with 32 percent identity over only 18 percent of the query length, with E-value = 4.

Metric Value % identity 32 % coverage 18 E-value 4

The most appropriate conclusion is:

  • A

    Higher E-values indicate stronger matches.

  • B

    The query is highly conserved across phyla.

  • C

    The match is likely due to chance and does not support meaningful homology.

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  • D

    The unknown sequence is a sea urchin gene.

Explanation

E-value of 4 means several random hits of this quality are expected by chance, low coverage and low identity reinforce that this is not a significant match.

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