问题 解答题

孟德尔在研究豌豆花颜色的杂交实验中发现,把白花植株与红花植株进行杂交,得到的后代(叫做子一代)全部为开红花的植株.如果子一代的红花植株自花传粉,再得到的后代(叫做子二代)中除红花植株外,又出现了白花植株.请你分析:红花与白花这对相对性状中,显性性状是______,隐性性状是______.若以“G、g“来表示这对基因,则亲代的红花基因组成为______,白花基因组成为______;子一代的红花基因组成为______;子二代的白花基因组成为______.

答案

红花植株与白花植株进行杂交,得到的后代(叫子一代)全部为红花植株,说明红是显性性状,白是隐性性状.子一代的基因来自杂交双方,因此其基因组成是Gg.子二代植株除红花植株外,又出现了白花植株,这种现象称为变异.在子二代中,红花的基因组成有两种情况,分别是GG或Gg;子二代红花植株出现的比例是75%.子二代的白花基因组成为gg,出现的比例为25%,如下图所示.  

 

故答案为:红花; 白花;GG;gg;Gg;gg

阅读理解

阅读理解。

     Mrs. White lived in a town of England. Her husband died three years ago and one of her children worked

in the capital and the other three lived in another town. Her husband didn't leave her much money and she had

to live a simple (简朴) life. Sometimes her children went to see her during their holidays, ubt they stayed with

her for only two or three days.

     One winter morning the old woman got up early. She was going to buy some food in a shop. And when

she came out, she found there was much snow in the street. She had to sweep it away. And suddenly she

found a dying dog at the corner of the house. She picked it up and took it into to house quickly. She put it near

the fire and gave it some milk and bread. At first the poor dog ate nothing and that afternoon it drank some milk

and three days later it was all right. Now the old woman found it was a beautiful dog. And she liked it very much

and took it everywhere she went. A week later she went shopping with her dog. At a bus stop a young man

was eating fish and chips. The little dog became very excited (兴奋) at the smell of the man's lunch and began

jumping up at him.

     "Do you mind if I throw it a bit (一点)?" asked the young man.

     "Not at all," answered Mrs. White.

     Having heard this, he picked up the dog and threw it over the wall.

1. Mrs. White lived a simple life because _____.

A. she wasn't rich enough

B. she hoped to save money for her children

C. she had four children

D. her children hated her

2. It was _____ that morning when Mrs. White went to buy something.

A. it was beautiful

B. it was little

C. she spent money on it

D. she felt lonely

3. The old woman liked the dog very much because _____.

A. it was beautiful

B. it was little

C. she spent money on it

D. she felt lonely

4. The dog hoped _____, so it became excited.

A. to be given some food

B. to leave the bus stop soon

C. to bite (咬) the young man

D. to go as soon as possible

单项选择题