题目

玉米种子颜色由三对等位基因控制，三对等位基因独立遗传。A、B、R基因同时存在时为有色，其余基因型都为无色。一棵有色种子的植株Z与三棵植株杂交得到的结果为（ ）AAbbrr×Z→有色：无色=1：1 aaBBrr×Z→有色：无色=1：3aabbRR×Z→有色：无色=1：1植株Z的基因型为（ ）A.AABBRr B.AaBBRr C.AaBbrr D.AaBbRR 答案：【答案】B【解析】1.基因型和性状的关系为：玉米有色种子必须同时具备A、B、R三个基因，否则无色，则有色种子的基因型是A_B_R_，其他基因型为无色；2.合理使用拆分法进行解答：①AAbbrr×Z→有色：无色=1：1，说明有色种子的比例为1/2×1×1；②aaBBrr×Z→有色：无色=1：3，说明有色种子的比例为1/4×1×1Some places in the world have strange laws. It’s important for you to know about them before going there. Whoever likes to chew gum(口香糖) may have to leave Singapore. The government really wants to keep the city clean and will fine you for chewing gum. Before you leave for the United Arab Emirates you’d better make sure you aren’t visiting during Ramadan(斋月). During that time you aren’t allowed to eat or drink in public. Tourists have been fined up to $275 for drinking in public. Lovers spend so much time kissing each other goodbye at train stations that trains often start late. This law — no kissing your lover goodbye at train stations – is rather old, and isn’t in use today in France. In Thailand it’s against the law to drive a car or motorcycle without a shirt on, no matter how hot it is. Punishments are different in different areas and can include warnings and tickets costing about $10. No joke -- the local police will stop you. Studies in Denmark have shown that cars with their headlights on are more noticeable by other drivers than those with their headlights off. Drivers there are required to leave their headlights on even during the day, or they may face a fine up to $100. Do you often buy things using coins? Don’t do it in Canada. The Currency Law of 1985 doesn’t allow using only coins to buy things. Even the use of the dollar-coin is limited (受限制的). The shop owner has the right to choose whether to take your coins or not. Make sure you know about these laws before your next trip. Better safe than sorry.小题1:What is mainly talked about in the text?A．How to make your trip around the world safe.B．Why there are strange laws in the world.C．Interesting places you can go to around the world.D．Some strange laws you should know about for your trip.小题2:If you are driving a car in Thailand, _____.A．the police will play a joke on youB．you should wear your shirt even though it’s hotC．the police will give you tickets costing about $10D．you should always keep your headlights on小题3:What can we learn from the text?A．Kissing goodbye at train stations isn’t allowed in France today.B．The Singaporean government cares a lot about its environment.C．Tourists in the United Arab Emirates shouldn’t eat in public.D．You can turn your headlights off in daytime in Denmark.小题4:What do we know about the strange law in Canada?A．It is a newly invented lawB．You aren’t allowed to use dollar-coins.C．You will be fined if you use coinsD．Shop owners can decide if you can use coins.