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The normal protein product of the RB gene acts as an inhibitor of transcription
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A、completely helpful
B、extremely useless
C、completely necessary
D、extremely normal
A、Hemoglobin in the red blood cells
B、Collagen in the extracellular compartment of the brain
C、A truncated neuronal protein
D、A misfolded form of a normal protein
E、A truncated extracellular protein
A、Nitrogen balance can reflect the metabolic status of protein in human body
B、Nitrogen balance refer to the relationship between nitrogen intake and nitrogen loss
C、Include normal nitrogen balance,positive nitrogen balance and negative nitrogen balance
D、For children and normal adults, nitrogen intake>nitrogen loss
What's the result of the French study?
A.The harm of mobile phone radiation is life-threatening.
B.Mobile phone radiation may affect one's normal way of thinking.
C.Sleep disorders could result from mobile phone radiation.
D.A protein called hsp27 is activated by mobile phone radiation.
What's the result of the French study?
A.The harm of mobile phone radiation is life-threatening.
B.Mobile phone may affect one's normal way of thinking.
C.Sleep disorders could result from mobile phone radiation.
D.A protein called hsp27 is killed by mobile phone radiation.
What's the result of the French study?
A.The harm of mobile phone radiation is life-threatening.
B.Mobile phone may affect one's normal way of thinking.
C.Sleep disorders could result from mobile phone radiation.
D.A protein called hsp27 is killed by mobile phone radiation.
Regimes that are proposed by people who do not look as if they enjoyed their food, and who do not themselves have a well-fed air, may not be ideal for normal people. Graham Lusk, who combined expert knowledge with a normal appreciation of good food, describes how he and Chittenden, who advocated a low-protein diet, spent some weeks in Britain eating the rations of the 1914-1918 war and then got more ample rations on board ship. Lusk attributed his sense of well-being to the extra meat he was eating; Chittenden attributed it to the sea air.
When young animals are reared for sale as meat, the desirable amount of protein in their food is a simple matter of economics. Protein is expensive, so the amount given is increased up to the level at which the increased rate of growth is offset by the increased cost of the diet. As already mentioned, the efficiency with which protein is used to build the body diminishes as the percentage of protein in the diet increases. In practice, the best diets seem to contain between 15 and 25 per cent protein. It is not certain that maximum growth rate is desirable in children; some experiments with rats suggest that rapid growth is associated with a shorter ultimate expectation of life.
There are practical and ethical obstacles to human experiments in which the effect of protein can be measured. Children do not grow as fast as the young animals in which there is a commercial interest. Their need for protein is therefore presumably smaller, but there is no evidence that the desirable protein level, after weaning, is less than 15 per cent. An argument against this percentage of protein is that in human milk only 13 per cent of the solid material is protein. That protein is, however, of better quality than any protein likely to be given to infants that are not weaned on cow's milk.
Furthermore, milk, like other products of evolution, is a compromise. Mothers are not expendable. A species would not long survive if mothers depleted their own proteins so much in the course of feeding the first child that the prospects of later children were seriously jeopardized. Human milk is no doubt a good food, but the assumption that it is necessarily ideal is stretching belief in the beneficence and perfection of Nature too far.
When considering nutritional statements, apart from statements that depend on observation, we should also consider______.
A.the strange low-protein diet
B.the unusual character of the observer
C.the unexpected meals provided by the observer
D.the ample rations of the 1914 - 1918 war
【单选题】A 2-year-old child presents with poor weight gain, sparse hair, unusual face with sunken eyes, and skin that reddens markedly in sunlight. A diagnosis of Cockayne syndrome (MIM*216400) is considered and studies of DNA synthesis are undertaken. In vitro assay of labeled thymidine incorporation reveals decreased levels of DNA synthesis compared to controls, but normal-sized labeled DNA fragments. The addition of protein extract from normal cells gently heated to inactivate DNA polymerase restores DNA synthesis in Cockayne cells to normal. Which of the following enzymes used in DNA replication is most likely to be defective in Cockayne syndrome?
A、Unwinding proteins
B、DNA-directed RNA polymerase
C、DNA polymerase I
D、DNA ligase
E、DNA-directed DNA polymerase
【单选题】Lipoproteins transport lipids from intestine and liver where they are absorbed and metabolized to peripheral tissues via the bloodstream. They contain core proteins (apo proteins) that bind various types of lipid, thus producing lipoprotein complexes of varying densities—very low density lipoproteins (VLDL), low density lipoproteins (LDL), and high density lipoproteins (HDL) after plasma lipoprotein electrophoresis. A disorder called abetalipoproteinemia (MIM*200100) was distinguished by its deficiency of the bands for very low density lipoproteins (VLDL) and low density lipoproteins (LDL) after plasma electrophoresis. Affected patients have ataxia (wide gait, incoordination), retinopathy (retinal degeneration with blindness), and myopathy (muscle weakness). VLDL and LDL contain the same apoB core protein, their different densities produced by association with different lipids, and apoB became good candidate for mutation in the disorder. Initial characterization of the apoB gene together with its mRNA and protein products demonstrated identical mRNA sizes in all tissues. Western blotting using antibody specific for the amino-terminus of apoB protein showed a 100-kDa species in liver and a 48-kDa species in intestine, as did antibody specific for the C-terminus of the 48-kDa intestinal protein. Molecular study of a patient with abetalipoproteinemia showed normal mRNA sizes, but 100-kDa peptide species were identified in both liver and intestine using the amino- or carboxy-terminus antibody probes. Which of the following processes is most likely deficient in this patient with apobetalipoproteinemia?
A、RNA splicing
B、DNA amplification
C、Transcription initiation
D、RNA editing
E、Transcription factor phosphorylation
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