To avoid being degraded by nuclear exonucleases, nascent transcripts, pre-mRNA-processing intermediates, and mature mRNAs in the nucleus must have their ends protected. Which of the following mechanism are present in the cell to protect mRNA from degradation?

I. The 5′ cap is protected because it is bound by a heterodimeric nuclear cap-binding complex (CBC), which protects it from 5′ exonucleases and also functions in export of the mRNA to the cytoplasm.

II. 5’-5’ phosphodiester bond in the cap of mRNA plays crucial role in protection

III. The 3′ end of a nascent transcript lies within the RNA polymerase and is thus inaccessible to exonucleases 

#Question id: 33105

#Unit 1. Molecules and their Interaction Relevant to Biology

#Question id: 572

#Unit 1. Molecules and their Interaction Relevant to Biology

Which of the following has not been shown to play a role in determining the specificity of protein kinases?

#Question id: 1860

#Unit 4. Cell Communication and Cell Signaling

Mendelian susceptibility to mycobacterial infection does NOT involve the gene for:

#Question id: 4000

#Unit 3. Fundamental Processes

Which statement is false about the utilization of lactose as a carbon source by E. coli?

#Question id: 1385

#Unit 4. Cell Communication and Cell Signaling

The ability of a population of fibroblasts to migrate along the surface of a tissue culture dish depends on adhesion between the cell surface and the extracellular matrix molecules coating the dish. The dish is coated with laminin, and the only cell-surface protein capable of binding laminin is a cell-adhesion protein called an integrin. Integrins are integral plasma-membrane proteins that function as heterodimers. Under these conditions the rate at which a fibroblast can migrate along the laminin coated culture dish is proportional to the strength of adhesion between the cell and the laminin substrate. The table below lists the rate of cell migration observed for fibroblasts genetically engineered to generate the indicated phenotypes.

 Which of the following is the most likely explanation for failure of overexpression of the integrin alpha subunit to alter the rate of fibroblast migration?