Site-Directed Mutagenesis of Tyr-15 to Phe in Cdc2

Question

Site-directed mutagenesis of Tyr-15 to Phe in cdc2:
A)results in the wee phenotype.
B)results in a phenotype similar to that caused by mutation in cdc25.
C)increases the possible number of phosphate groups on Cdc2.
D)prevents binding of Cdc13.

Accepted Answer

The substitution of tyrosine with phenylalanine at position 15 in cdc2 confers a wee phenotype, characterized by early entry into mitosis, shortened G2 phase, and small cell size. This mutation prevents tyrosine dephosphorylation of cdc2, which is necessary for its activation by cyclin-dependent kinase-activating kinase (CAK). Therefore, cdc2 remains active throughout the cell cycle, driving cells into mitosis prematurely. This phenotype is similar to that caused by mutations in cdc25, a phosphatase that dephosphorylates cdc2 on tyrosine 15.