相关考题
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单项选择题
某市1998年社会商品零售额为12000万元，2002年增至15600万元，这四年中物价上涨了4%，则商品零售量指数为( )。 A．130% B．104% C．80% D．125%
A.130%
B.104%
C.80% -
未知题型
甲横穿马路,被一辆出租车撞死,甲死亡后遗产由其法定继承人继承,该继承法律关系产生的法律事实为( )
A.事件、行为
B．行为、事件
C．事件、事件
D．行为、行为 -
未知题型
Nearly a century ago, biologists found that if theyseparated an invertebrate animal embryo into two partsat an early stage of its life, it would survive and developas two normal embryos. This led them to believe that the(5) cells in the early embryo are undetermined in the sensethat each cell has the potential to develop in a variety ofdifferent ways. Later biologists found that the situationwas not so simple. It matters in which plane the embryois cut. If it is cut in a plane different from the one used(10) by the early investigators, it will not form. two wholeembryos.A debate arose over what exactly was happening.Which embryo cells are determined, just when do they-become irreversibly committed to their fates, and what(15) are the “morphogenetic determinants” that tell a cellwhat to become? But the debate could not be resolvedbecause no one was able to ask the crucial questionsin a form. in which they could be pursued productively.Recent discoveries in molecular biology, however, have(20) opened up prospects for a resolution of the debate.Now investigators think they know at least some of themolecules that act as morphogenetic determinants inearly development. They have been able o show that,in a sense, cell determination begins even before an egg(25) is fertilized.Studying sea urchins, biologist Paul Gross foundthat an unfertilized egg contains substances that func-tion as morphogenetic determinants. They are locatedin the cytoplasm of the egg cell; i.e., in that part of the(30) cell’s protoplasm that lies outside of the nucleus. In theunfertilized egg, the substances are inactive and are notdistributed homogeneously. When the egg is fertilized,the substances become active and, presumably, governthe behavior. of the genes they interact with. Since the(35) substances are unevenly distributed in the egg, when thefertilized egg divides, the resulting cells are differentfrom the start and so can be qualitatively different intheir own gene activity.The substances that Gross studied are maternal(40) messenger RNA’s --products of certain of the maternalgenes. He and other biologists studying a wide varietyof organisms have found that these particular RNA’sdirect, in large part, the synthesis of histones, a classof proteins that bind to DNA. Once synthesized, the(45) histones move into the cell nucleus, where section ofDNA wrap around them to form. a structure that resem-bles beads, or knots, on a string. The beads are DNAsegments wrapped around the histones; the string is theintervening DNA. And it is the structure of these beaded(50) DNA strings that guides the fate of the cells in whichthey are located.It can be inferred from the passage that the morphogenetic determinants present in the early embryo are______A．located in the nucleus of the embryo cellsB．evenly distributed unless the embryo is not developing normallyC．inactive until the embryo cells become irreversibly committed to their final functionD．identical to those that were already present in the unfertilized eggE．present in larger quantities than is necessary for the development of a single individual
A.
A
B.
Which
C.
Recent
D.
Now
E.
Studying
F.e.,
G.
The
H.
It
I.located
J.evenly
K.inactive
L.identical
M.present
