Use the Following Information When Answering the Corresponding Questions)

question 16

Multiple Choice

Use the following information when answering the corresponding questions) .
A group of enzymes known as cytosine- specific DNA methylases recognize CpG dinucleotide sequences-that is, a cytosine followed by a guanosine G) in one DNA strand-and add methyl groups to the cytosine. Many proteins bind to methylated CpG, including the methyl- CpG binding protein 2 MeCP2) . MeCP2 binding leads to the formation of a closed state of chromatin, thus silencing gene expression. A recent paper by Chen et al. reported an interesting mechanism of regulating transcription of a gene via MeCP2 W. Chen, Q. Chang, Y. Lin, A. Meissner, A. E. West, E. C. Griffith, R. Jaenish, and M. Greenberg. 2004. Derepression of BDNF transcription involves calcium- dependent phosphorylation of MeCP2, Science 302:885-89) . This gene, called BDNF, encodes brain- derived neurotrophic factor BDNF) -a protein that plays an important role in nerve cell and central nervous system function, including memory and learning. Remarkably, most cases of Rett syndrome, an important cause of mental retardation in females, are due to loss- of- function mutations of MeCP2.
-Elsewhere in the paper, Chen et al. state that "BDNF is encoded by a complex gene with four well- characterized promoters that give rise to at least eight different mRNAs." What mechanism could account for the production of these different BDNF mRNAs?

• A) alternative splicing
• B) translational control
• C) post- translational control
• D) chromatin condensation control

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