题干

老鼠毛色有黑色和黄色,这是一对相对性状,由一对等位基因控制。有下面三组交配组合,在四个亲本中是纯合子的是(    )

A:甲和丁

B:乙和丙

C:丙和丁

D:甲和乙

上一题 下一题 0.0难度 选择题 更新时间:2011-03-11 04:12:55

答案(点此获取答案解析)

A

同类题2

阅读理解

    Hello,everybody.Welcome to surf on a new Web site—SCIENCE NEWS FOR KIDS!

    Our goal is to offer timely items of interest to kids,accompanied by suggestions for hands on activities,books, articles,Web resources,and other useful materials.

    Our emphasis is on making the Web site attractive by offering kids opportunities to comment on and grade the subject matter,get ideas for science projects,and try out math puzzles.At the same time,we offer teachers creative ways of using science news in their classrooms.

    The Science News for Kids Web site,supported by several corporations and foundations,strengthens the usefulness of Science News in the middle-school classroom and offers entertaining reading and activities for students interested in science.

    A section of the Science News for Kids Web site is devoted to particular interests.At present,we have six such zones: a weekly brainteaser(难题)for those who enjoy solving and inventing puzzles (PuzzleZone),entertaining science-fiction composition exercises for those interested in writing (SciFiZone),and weekly science short description along with science project ideas and tips (ScienceFairZone).The GameZone contains a small selection of logic and memory games.The TeacherZone has materials,including question sheets related to the feature article of the week,so that teachers can bring science news topics to the classroom.The LabZone features a weekly hands on activity or science project idea.In the future,we might add additional zones,for example,for kids interested in robotics,the environment,computers,math,or veterinary(兽医的)medicine and animals.

    Contact us at editor@snkids.com.         Science News for Kids            1719 N Street,N.W.

    Washington,DC 20036                 Phone :202-785-2255             Fax: 202-659-0365