问题 单项选择题

如果一对夫妇生一个色盲女儿的可能性为1/4,则这对夫妇的基因型为()

A.XBXBXBY

B.XBXBXbY

C.XBXbXbY

D.XbXbXBY

答案

参考答案:C

解析:

伴X染色体隐性遗传病发病特点:男患者多于女患者;男患者将至病基因通过女儿传给他的外孙(交叉遗传)。基因型为XBXB和XBY的夫妇生一个色盲女儿的几率为0;基因型为XBXB和XbY的夫妇生一个色盲女儿的几率为0;基因型为XBXb和XbY的夫妇生一个色盲女儿的几率为1/4;基因型为XbXb和XBY的夫妇生一个色盲女儿的几率为0。所以选C。

考点:伴性遗传

点评:本题难度一般,要求学生能运用基因的分离定律和伴性遗传的相关知识分析实际问题。

判断题
阅读理解

     Here is a poster- on a middle school web site. Read the web-site poster.                      

     Going, Going, Gone!

    The Haynes Middle School Parent-teacher Organization

     nvites you to attend our latest fund (基金) -raiser

    The Fourth Annual (每年一次) Haynes School Auction(拍卖)

     Saturday, May 10

     6:00 p.m.--11:00 p.m. in the school hall

     6:00 p.m.--6:30 p.m.: All items for auction are previewed(预览).

     6:30 p.m.--7:00 p.m.: Silent auction begins.

     7:00p.m.--7:30p.m.: Highest bidders(出价人) from silent auction are determined.

     7:30--11:00 p.m.: Main auction begins.

     Items up for bid in the silent auction list in value from $ 5.00 to $ 30.00

     Items up for bid in the main auction include the following;

    1. Airline tickets to a place of your choice

    2. Weekend getaways at first-class hotels

    3. Season tickets to the Chicago Bears football game

    4. $ 50 gift tickets to local gift shops, restaurants, and salons

    5. Theater tickets to The Merchant of Venice

    Don't miss the boat! Book your tickets today.

     Last year, tickets sold out in five days!

     Tickets are sold on a first-come, first-served basis.

      $15.00 per person

     All the money from the auction will be given to the Haynes School computer lab.

1. Which of the following is not mentioned as being up for bid at the auction?

A. A movie pass to the local cinema.  

B. A weekend stay at a hotel.

C. A ticket to a restaurant.          

D. Airline tickets.

2. The more items that are given or bought for auction,             

A. the less money that will be charged for the tickets to the auction

B. the more money that can be raised to support the computer lab

C. the faster the ticket will be sold to the auction

D. the higher the value that will be placed on the items in the silent auction

3. The phrase" first-come, first-served" tells you that          

A. people can buy the tickets on the first day onl

B. the person who is first to arrive will receive a ticket at no charge

C. food and drinks will be served at the auction

D. tickets are sold in the order of who arrives first to buy them

4. Which of the following is most likely to happen at the year's auction?

A. The airline tickets will receive higher bids than any other item.

B. All items up of bid will be sold for at least twice their value.

C. More money will be raised this year than in any other year before.

D. Tickets for the event will be sold out in less than one week.

5. When dose the main auction begin?

A. 7.00p.m.--7.30p.m.              

B. 6.30p.m.--7.00p.m.

C.7.30p.m.--11.00p.m.          

D. 6.00p.m.--6.30p.m.