Use the Following Information to Answer the Question

question 56

Multiple Choice

Use the following information to answer the question.
In an investigation into sperm-oocyte binding, researchers isolated the egg receptor protein, ERB1, from the sea urchin Strongylocentrotus purpuratus. ERB1 binds to the sperm acrosomal protein, bindin, during fertilization. The researchers coupled the ERB1 receptor from S. purpuratus to plastic microbeads and then mixed the ERB1-coupled beads with sperm from S. purpuratus or from the related species, S. franciscanus. A summary of the treatment mixtures and a graph of the results are shown.
Treatments:
A: S. purpuratus sperm mixed with S. purpuratus ERB1-coupled beads
B: S. purpuratus sperm mixed with beads with no coupled ERB1 protein
C: S. franciscanus sperm mixed with S. purpuratus ERB1 beads
D: S. franciscanus sperm mixed with beads with no coupled ERB1 protein
Which of the following conclusions is most consistent with the data?

• A) Plastic beads do not bind at all to sperm from either species of sea urchin.
• B) ERB1 prevents S. franciscanus sperm from binding the beads.
• C) Sperm from S. purpuratus bind to beads more if ERB1 is present than if ERB1 is not present.
• D) S. franciscanus and S. purpuratus are the same species.

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