单选题达尔文是怎样解释进化如何发生的( )。

单选题某些转座过程中 ____ 是作为一种中间体存在的。

单选题右图谱系中，涂黑者为带有性状W的个体，这种性状在群体中是罕有的。如下哪种情况是与谱系中W的传递情况一致的?(a)常染色体隐性；(b)常染色体显性；(c)X连锁隐性；(d)X连锁显性；(e)Y连锁。

单选题曼陀罗有12对染色体，已发现12种(2n+1)的三体类型．那么“2n+1+1”型可能有______种。 A．256种 B．44种 C．24种 D．66种

单选题现有ABCD四个玉米自交系，其中A和D是姐妹自交系，B和C是姊妹自交系，四个自交系可以配成6个单杂种，为了使双杂种的杂种优势强，你将选择哪两个单交种进行杂交?( )

单选题原核RNA pol识别的启动子位于 a．转录起始点的上游； b．转录起始点的下游； c．转录终点的下游； d．无一定位置。

单选题单倍体链孢霉一般是粉红色，白色是他的突变型，如果把粉红色链孢霉与白色进行杂交，其子是粉红色的概率是______。 A.100% B.3/4 C.1/2 D.1/4

单选题黄子叶、圆粒、白花与黄子叶、圆粒、红花豌豆杂交，后代黄、圆、红31，黄、圆、白29，黄、皱、红11，黄、皱、白9。已知黄、圆、红为显性，请选择:

单选题哈迪-温伯格定律表示群体在逐代中的遗传平衡，这一定律的数学表示为( )。

单选题酵母DNA的A+T/G+C为2，则A/G、A/C、A/T应分另0为( )。

单选题Electronics are being recycled in record numbers as more states require it and more companies collect and even pay for discarded items, but the gains come with controversy. Some environmentalists complain that recycling is not keeping pace with electronics sales. Some say e-waste is being dumped in developing countries, where toxic materials such as lead and mercury can leach from landfills into groundwater. "It is a success story, but we'd like to see it get more successful" to keep up with the electronics boom, says Janette Petersen of the Environmental Protection Agency (EPA). The amount of recycled items more than doubled from 1999 to 2007, the most recent year for which the EPA has figures. But as a percentage of all electronics, it increased less, from 15% to 18%. "The demand for electronics recycling has been growing," partly because of the switch last year to digital TV, says Jennifer Berry of Earth911. corn, a private group that keeps a database of recyclers. Last year, she says 31% of inquiries involved electronics, primarily TVs, batteries and computers. Public and private efforts are expanding. Vermont became the 21st state last month to enact a law that requires e-waste recycling. Twenty-six companies--including Dell, Hewlett Packard, ATT and Verizon--have partnered with the EPA on the Plug-In to eCycling program to promote electronics recycling since its launch in 2003. Companies such as Gazelle. corn pay for used gadgets such as iPods, which they resell or recycle. Best Buy and other stores are collecting more e-waste. Target announced last month that it put bins in every store to accept cellphones, MP3 players and ink cartridges. Jim Puckett of Basel Action Network, a Seattle-based non-profit organization that aims to stop toxic exports, worries that some American companies dump e-waste in Africa to save money. "People are trying to look green, but they're not telling you where it (waste) is going," he says. "You can't turn over your TV to just any recycler. " He says it's better to store an old TV than give it to a recycler that may export it to poor countries. The Basel Action Network announced its e-Stewards program last month to ensure safe handling of electronics by using only recyclers certified by accredited organizations. It now lists 45 recyclers in 80 locations. Samsung and other companies have signed on. Environmental groups, including the Sierra Club, back it.

单选题核型为48，XXXX的女性，她的巴氏小体有______。 A.一个 B.二个 C.三个 D.四个

单选题用中性小菌落与分离型小菌落的酵母杂交，经减数分裂后所得子代分离比是 ____ 。

单选题为了确定T4噬菌体的h和r位点间的重组率，利用大量的h+r-和h-r+噬菌体对E.coli进行复感染，收集裂解液，分析其基因型，结果是：h+r+=2000；h+r-=3000；h-r+=3000；h-r-=2000，这些资料说明两位点间的重组率是______ A.40% B.75% C.57% D.60% E.上述答案均不对

单选题相互易位杂合体自交，子代中将有______比例的易位纯合体。 A．0 B．15/% C．50/% D．25/%

单选题以下哪种情况不属于同源重组? ____

单选题某植物体细胞内只有一套染色体，所以它是______。 A．一倍体 B．缺体 C．单价体 D．单体