几题(?!)生物想请教各位..不好意思麻烦了...谢谢... snRNA are synthesized in the (A)cytoplasm and function in the nucleus (B)nucleus,move to the cytoplasm to pick up proteins to become functional,and them return to the nucleus The human genome contains only 20000 to 25000 actual gene sequences,yet the human genome can produce up to 30000 gene products . which of the following accounts for this difference? (A)alternative splicing (B)exon shuffling (C)short interspersed elements(SINEs) which of the following is not characteristic of a eukaryotic enhancer element (A)its activity is indepenndent of its orientation(the sequence can be inverted without effect) (B)it may be positioned at the 5end or the 3end of the gene which of the following describes ubiquinone? (A)a small hydrophobic coenzyme (B)a protein in the electron transport chain when muscle cells undergo anaerobic respiration,they become fatigated and painful.this is now known to be caused by (A)increase in potassium ions (B)buildup of lactate which of the following is the best explanation for the inability of the animal cell to reduce the Ca2+ concentration in its cytosol compared with the extracellular fluid (A)insufficient ATP levels in the cytoplasm (B)blockage of the synaptic signal (C)loss of transcription factors (D)low oxygen concentration around the cell (E)low level of protein kinase in the cell where do the mcrotubules of the spindle originate during mitosis in both plant and animal cells (A)centrosome (B)centromere (C)centriole (D)chromatid (E)kinetochore The nuclear-synthesized poly-A sequence at the 3 end of eukaryotic messenger RNA is (A)found also as a common feature in rRNA and tRNA (B)transcribed by rna polymerase 2 .. --

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