问题 解答题

人的有耳垂由显性基因D控制,无耳垂由隐性基因d控制.下表为李强家族中三代人的耳垂遗传情况.请据表回答:

成员爷爷奶奶爸爸妈妈李强
性状表现有耳垂有耳垂有耳垂有耳垂无耳垂
(1)若李强的爸爸妈妈再生一个孩子,则该孩子控制耳垂的基因组成可能有______种,表现为有耳垂的可能性是______.

(2)下列对该家族遗传情况叙述不正确的是______

A.李强父母的基因组成都是Aa

B.李强父母再生一个女孩的可能性是50%

C.李强爷爷和奶奶的基因组成都是AA

D.李强爷爷的基因组成可能是Aa或AA

(3)若图为该家族中某人体细胞的染色体图,则其产生的生殖细胞的染色体组成为______.

答案

(1)由显性基因控制的性状是显性性状,由隐性基因控制的性状是隐性性状;在耳垂的有无这对相对性状的遗传中,小明出现了他的父母没有的性状,说明无耳垂是隐性性状,由隐性基因控制,那么有耳垂为显性性状,由显性基因控制.若用A表示显性基因,a表示隐性基因,则这对基因的遗传图解如图所示:则无耳垂的小明的基因组成是aa,其父母的基因组成都是Aa.若李强的爸爸妈妈再生一个孩子,则该孩子控制耳垂的基因组成可能有AA或Aa

(2)生物体的某些性状是由一对基因控制的,而成对的基因往往有显性显性和隐性之分,当细胞内控制某种性状的一对基因,一个是显性、一个是隐性时,只有显性基因控制的性状才会表现出来;当控制某种性状的基因都是隐性基因时,才会表现出隐性性状.由于李强父母的基因组成都是Aa,所以李强爷爷和奶奶的基因组成不可能都是AA,这样的条件下,李强的基因组合就是AA,与实际情况不符.故选C符合选项.

(3)若图为该家族中某人体细胞的染色体图,第23对性染色体形态大小都一样,则其产生的生殖细胞的染色体组成为X.

故答案为:(1)2;AA或Aa (2)C;(3)X

阅读理解

阅读短文,根据其内容回答问题。

     I was shopping in the supermarket when I heard the young voice. 

     "Mom, come here! There's this lady here my size!"

     The mother rushed to her son; then she tumed to me to say "sorry".

     I smiled and told her, "It's okay." Then I talked to the boy, "Hi, I'm Darryl Kramer. How are you?"

     He studied me from head to toe, and asked, "Are you a little mommy?"

     "Yes, I have a son," I answered.

     "Why are you so little?" he asked.

     "It's the way I was bom," I said, "some people are little. Some are tall. I'm just not going to grow any

bigger." After I answered his other questions, I shook the boy's hand, and left.

     My life as a little person is filled with stories like that. I enjoy talking to children and explaining why I

look different from their parents. I stand 114 cm tall. I was born an achondroplasia dwarf (侏儒). Despite

this, I did all the things other kids did when I was growing up.

     I didn't realize how short I was until I started school. Some kids picked on me, calling me names (辱骂

我). Then I knew I began to hate the first day of school each year. New students would always look fixedly

at me as I tried hard to climb the school bus stairs.

     But I learned to smile and accept the fact that I was going to be noticed my whole life. I decided to make

my uniqueness (与众不同) an advantage rather than a disadvantage. What I lacked (缺少) in height, I made

up for in personality.

     I'm 47 now,and people are surprised when they see me driving. I try to keep a good attitude. When people

are not polite enough, I say to myself, "Look what else I have-a great family, nice friends."

     It's the children's questions that make my life special. I enjoy answering their questions. My hope is that,

I will encourage them to accept the persons around them, whatever size and shape they come in, and treat

them in a friendly way.

1. Did the writer answer the little boy's questions in the supermarket?

    ______________________________________________________________________

2. How tall is the writer? 

    ______________________________________________________________________

3. When did the writer realize how short she was?

    ______________________________________________________________________

4. What did the writer want to teach the children when she answered their questions?

    ______________________________________________________________________

5. What is the writer's attitude to her life? 

    ______________________________________________________________________

单项选择题