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The 5' cap on eukaryotic mRNA molecules is recognized by which of the following proteins?
The 5' cap is recognized by the important translation factor eIF4e. Once bound, eIF4e helps transport the mRNA molecule to the ribosome and facilitates bonding to the ribosomal machinery.
The 3' poly-A tail is recognized by PABP. RNA polymerase is involved in transcription, not translation. The 40s ribosomal subunit is recruited by the initiation complex (including eIF4e, PABP, and various other translation factors).
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When conducting a stain of chromosomes, certain regions along the chromosome will stain more darkly than the rest. This is due to the fact that these regions are more tightly condensed. What is the functional outcome of having one region more condensed (heterochromatin) than the rest (euchromatin)?
Heterochromatin often contains simple, repetitive sequences, and although it cannot be said that it is completely void of coding sequences, it is not typically transcribed. The tight wrapping prevents polymerase from accessing the strand, and euchromatin typically contains the regions that get transcribed. Thus, heterochromatin is though to contain repressed or inactive genes.
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Small GTPases are important molecular switches and signaling pathways. What proteins are responsible for promoting the activation of these small GTPases?
The correct answer is guanine nucleotide exchange factors. In order to activate small GTPases and subsequently stimulate downstream pathways, guanine nucleotide exchange factors bind inactive GTPases and cause the release of guanine diphosphate (GDP). This allows guanine triphosphate (GTP) to bind and active the GTPase.
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