Mitotic CDK complexes are maintained in an inactive state through inhibitory phosphorylation of the CDK subunit. Two highly conserved tyrosine and threonine residues in mammalian CDKs are subject to regulated phosphorylation.

Gene	Mutant phenotypes
A. Wee1	i. the cell does not divide but continues to grow
B. CAK kinase	ii. mitotic cyclins are inactivated
C. cdc25 phosphatase	iii. premature entry into mitosis

The following table enlists genes and phenotypes observed on mutation of these genes but not correctly matched. Which one of the following combinations is correctly matched ?

#Question id: 4076

#Unit 3. Fundamental Processes

RNA-binding proteins

a. can be identified by chromatography of UV irradiated nuclear extracts over oligo-dT columns.

b. can be identified by sequence homology to known RNA-binding domains.

c. have a conserved structure as seen by X-ray crystallographic analysis.

d. alter the secondary structure of pre-mRNAs, which decreases interactions with other RNAs or proteins.

e. always remain in the nucleus.

#Question id: 4077

#Unit 3. Fundamental Processes

Which of the following is (are) associated with most polyadenylation events?

a. cleavage of the 5´ end of the RNA molecule

b. an assembly of a large, multiprotein complex

c. the AAUAAA site upstream of where polyadenylation will occur

d. a GU-rich or U-rich region near the cleavage site

e. slow addition of A residues followed by rapid addition of 200 to 250 more A residues

#Question id: 4078

#Unit 3. Fundamental Processes

Which of the following is (are) required for splicing to occur?

a. two transesterification reactions

b. intact, naturally occurring introns

c. formation of a lariat like structure

d. a branch-point G residue

#Question id: 4079

#Unit 3. Fundamental Processes

What is the evidence that pre-mRNAs are not synthesized unless machinery for processing is properly positioned?

#Question id: 4080

#Unit 3. Fundamental Processes

How the location of exons and introns within a gene are determined?

#Question id: 4081

#Unit 3. Fundamental Processes

Which of the following regulatory scenarios of cell-type-specific expression of fibronectin isoforms in humans is (are) consistent with information on known splicing factors?

a. A Tra-like splicing factor expressed in fibroblasts is required for inclusion of EIIIA and EIIIB exons.

b. An Sxl-like splicing factor is required in hepatocytes for exclusion of EIIIA and EIIIB exons.

c. A Tra-2-like factor enhances binding of the cleavage/polyadenylation complex in fibroblasts.

d. A Dsx-like protein is required to inhibit transcription of the fibronectin gene.