MPF activity was discovered when cytoplasm from a Xenopus M-phase cell was injected into Xenopus oocytes, inducing the oocytes to form a mitotic spindle
In a control experiment, Xenopus interphase cytoplasm was injected into oocytes and shown not to induce the formation of a mitotic spindle. Which of the following statements is not a legitimate conclusion from the control experiment?
(a) The piercing of the oocyte membrane by a needle is insufficient to cause mitotic spindle formation.
(b) An increased volume of cytoplasm is insufficient to cause mitotic spindle formation.
(c) Injection of extra RNA molecules is insufficient to cause mitotic spindle formation.
(d) Components of an interphase nucleus are insufficient to cause mitotic spindle formation.
(d) The interphase cytoplasmic extract used as the control would not have contained nuclear components (because the nuclear membrane was intact) and so one cannot conclude that components of an interphase nucleus are insufficient to cause mitotic spindle formation. The other statements are all true.
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