单选题 用根癌农杆菌作载体转化植物细胞时，不适宜作受体的材料是： A、叶圆片 B、茎切段 C、新分离的原生质体 D、培养2~3天的原生质体

单选题决定紫茉莉花斑遗传的是______。 A.染色体 B.线粒体 C.叶绿体 D.卡巴粒

单选题下列突变哪个属于转换______。 A．A→G B．G→T C．C→G D．T→A

单选题It seemed so promising—mirrors sprawled across desert land in the scorching southwest delivering clean electricity and helping Americans out of the increasing fuel crisis. Some scientists and industry developers claim that Nevada's empty and sun-drenched expanses alone could supply enough electricity to power the entire country. Now even the optimists fear this wonderful prospect may be a mirage. Congress cannot make up their mind to extend the tax-reducing bill for solar-energy projects, which solar advocates say is critical to the future of their industry but which is due to expire at the end of the year. The latest attempt failed in the Senate earlier this month, prospects for a deal before November's presidential and congressional elections now look dim. Uncertainty has led some investors to delay or abandon projects in the past few months. Rhone Resch, the president of the Solar Energy Industries Association, said if the tax-reducing bill is allowed to expire at the end of the year, "it will result in the loss of billions of dollars in new investments in solar. " Further dampening hopes for a big solar-energy boom, the federal Bureau of Land Management (BLM) has abruptly suspended new applications to put solar collectors on federal land. The agency says it has received more than 130 applications and needs to conduct a region-wide environmental impact study on the industry before it will accept any more. The study will take 22 months to complete, however. Few argue against trying to preserve precious water sources and protect desert tortoises and other creatures that might not enjoy cohabiting with sprawling fields of mirrors. But many solar advocates wonder why the government is not acting as cautiously when it comes to drilling for oil and gas. Senator Maria Cantwell, a Democrat from Washington State, wants a congressional probe into the proposed suspension. "The fact that the BLM pops this out without people even knowing about it, especially when solar thermal looks extremely promising as a power source, is not right," she says. Harry Reid of Nevada, who is the majority leader in the Senate, also condemns the BLM's freeze, saying that it could "slow new development to a crawl". The BLM is not without its supporters, however. At a public meeting on June 23rd in Golden, Colorado, Alex Daue, of the Wilderness Society, said that his organization supports renewable energy development as long as it doesn't damage other important resources. The message is clear: no rubber stamps, even for renewable energy.

单选题有关物种的叙述正确的是( )。 ①一个种群就是一个物种；②具有一定的形态结构和生理功能，能相互交配且产生可育后代的一群生物个体；③隔离是新物种形成的必要条件；④在物种形成的过程中，地理隔离和生殖隔离是同时出现的

单选题单基因控制的某一相对性状，其杂合子表现为双亲的中间类型，其可能存在的魁固作用是

单选题人类的白化病是常染色体单基因隐性遗传病，两个都是白化病基因携带者的男女结婚，他们的孩子患白化病的概率是

单选题 下面哪个不是trp操纵子的调控成分？ A、操纵基因 B、前导序列 C、弱化子 D、增强子

单选题E. coli的lac基因是典型的负调节操纵子，在适当的底物存在时可以合成其产物β-半乳糖苷酶。当培养基中存在IPTG(isopropylthio galactoside)时 a．lac Z不表达； b．lac Y不表达； c．lac A不表达； d．lac Z、lac Y、lac A皆表达。

单选题按照达尔文的自然选择学说，下列叙述正确的是( )。

单选题一个女人的父亲是色盲，她的兄弟中有两人和一个舅舅是血友病患者，如果这个女人有一个血友病的患儿

单选题白眼雌蝇与红眼雄蝇杂交，后代出现白眼雌蝇的概率是 ____ 。

单选题新物种形成的必要条件是( )。

单选题下列哪一因素决定生物进化的方向( )。

单选题一个女人的父亲是色盲，她的兄弟中有两人和一个舅舅是血友病患者如果这个女人有一个血友病的患儿

单选题一对等位基因，在杂合的情况下，两种基因的作用都可以完全表现出来，这称为______。

单选题质核互作型雄性不育系的恢复系基因型为______。 A．S(RR) B．N(rr) C．S(rr) D．N(RR) E．A和D