In the Nematode Roundworm Caenorhabditis Elegans, the LIN-14 Protein Controls

question 29

Essay

In the nematode roundworm Caenorhabditis elegans, the LIN-14 protein controls the timing of certain cell divisions during development. LIN-14 protein levels are normally high in early development but decrease in the later stages. In a lin-4 mutant, the level of LIN-14 protein stays high throughout development, changing the pattern of cell divisions in the animal and producing defects in the shape of the animal. The lin-4 gene encodes a microRNA that binds to a sequence in the 3'UTR of the lin-14 mRNA.
a. How does the lin-4 microRNA likely regulate LIN-14 protein levels? Explain why the lin-4 mutant has high levels of LIN-14 throughout development.
b. Mutations in the 3' UTR of lin-14 have been identified that alter the sequence to which lin-4 normally binds. What effect would these mutations be expected to have on the expression of LIN-14 protein in the animal?

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