未知题型 将T4噬菌体的不同rⅡ突变株两两配对，在E．coli中对其顺式和反式均进行检验。然后比较其“裂解量”(每个细菌裂解后释放的噬菌体数)。关于6个不同的r突变——rU，rV，rW，rX，rY和rZ的结果如下表所示： 如果我们假定rV在顺反子A上，那么其他5个rⅡ突变是在顺反子A还是B上?

问答题 有一种南瓜平均重2．5 kg，另一个品种平均重1 kg。两个品种的杂交后代(F1)平均重1．75 kg。F1之间杂交得到200个F2，质量在1～2．5 kg之间，其中3个重2．5 kg左右，3个重1 kg左右。有多少对基因控制这两种南瓜的质量?每一对基因有多大的作用?

单项选择题 第一篇 Crystal Ear One day a friend asked my wife Jill if I wanted a hearing aid. 'He certainly does, 'replied Jill. After hearing about a remarkable new product, Jill finally got up the nerve to ask me if I'd ever thought about getting a hearing aid. 'No way,' I said. 'It would make me look 20 years older.' 'No, no,' she replied. 'This is entirely different. It's Crystal Ear!'Jill was right. Crystal Ear is different--not the old-styled body worn or over-the-ear aid, but an advanced personal sound system so small that it's like contacts (隐性眼镜) for your ears. And Crystal Ear is super-sensitive and powerful, too. You will hear sounds your ears have been missing for years. Crystal Ear will make speech louder, and the sound is pure and natural.I couldn't believe how tiny it is. It is smaller than the tip of my little finger and it's almost invisible when worn. There are no wires, no behind-the-ear device. Put it in your ear and its ready-to-wear mold (形状) fits comfortably. Since it's not too loud or too tight, you may even forget that you're wearing it! Use it at work or at play. And if your hearing problem is worse in certain situations, use Crystal Ear only when you need it.Hearing loss, which occurs typically prior to teenage years, progresses throughout one's lifetime. Although hearing loss is now the world's number one health problem, nearly 90 percent of people suffering hearing loss choose to leave the problem untreated. For many millions, treating hearing loss in a conventional way can involve numerous office visits, expensive testing and adjustments to fit your ear. Thanks to Crystal Ear, the 'sound solution' is now convenient. Almost 90 percent of people with mild hearing loss, and millions more with just a little hearing drop-off (下降), can be dramatically helped with Crystal Ear. Moreover, its superior design is energy-efficient, so batteries can last months. Crystal Ear is now available to help these people treat their hearing loss with a small hearing amplifier (放大器). 第 31 题 Initially the writer did not want to buy a hearing aid becauseA． it would make him look old.B． it would make him nervous.C． it was too expensive.D． it was old-styled.