问题 多选题

果蝇中,正常翅(A)对短翅(a)显性,此对等位基因位于常染色体上;红眼(B)对白眼(b)显性,此对等位基因位于X染色体上。现有一只纯合红眼短翅的雌果蝇和一只纯合白眼正常翅雄果蝇杂交,你认为杂交结果正确的是[ ]

A.F1代中无论雌雄都是红眼正常翅

B.F2代雄果蝇的红眼基因来自F1代的父方

C.F2代雄果蝇中纯合子与杂合子的比例相等

D.F2代雌果蝇中正常翅个体与短翅个体的数目相等

答案

AC

解答题
阅读理解

阅读理解

     I'm usually fairly skeptical about any research that concludes that people are either happier or

unhappier or more or less certain of themselves than they were 50 years ago. While any of these

statements might be true, they are practically impossible to prove scientifically. Still, I was struck by

a report which concluded that today's children are significantly more anxious than children in the 1950s.

In fact, the analysis showed, normal children ages 9 to 17 exhibit a higher level of anxiety today than

children who were treated for mental illness 50 years ago.

     Why are America's kids so stressed? The report cites two main causes: increasing physical

isolation-brought on by high divorce rates and less involvement in community, among other things-and

a growing perception that the world is a more dangerous place.

     Given that we can't turn the clock back, adults can still do plenty to help the next generation cope.

     At the top of the list is nurturing (培育) a better appreciation of the limits of individualism. No child

is an island. Strengthening social ties helps build communities and protect individuals against stress.

     To help kids build stronger connections with others, you can pull the plug on TVs and computers.

Your family will thank you later. They will have more time for face-to-face relationships, and they will

get more sleep.

     Limit the amount of virtual (虚拟的) violence your children are exposed to. It's not just video games

and movies; children see a lot of murder and crime on the local news.

     Keep your expectations for your children reasonable. Many highly successful people never attended

Harvard or Yale.

     Make exercise part of your daily routine. It will help you cope with your own anxieties and provide

a good model for your kids. Sometimes anxiety is unavoidable. But it doesn't have to ruin your life.

1. What does the author mean when he says, "we can't turn the clock back" (Line 1, Para. 3)?

A. It's impossible to slow down the pace of change.

B. The social reality children are facing cannot be changed.

C. Lessons learned from the past should not be forgotten.

D. It's impossible to forget the past.

2. According to an analysis, compared with normal children today, children treated as mentally

    ill 50 years ago ________.

A. were less isolated physically

B. were probably less self-centered

C. probably suffered less from anxiety

D. were considered less individualistic

3. The first and most important thing parents should do to help their children is ________.

A. to provide them with a safer environment

B. to lower their expectations for them

C. to get them more involved socially

D. to set a good model for them to follow

4. What conclusion can be drawn from the passage?

A. Anxiety, though unavoidable, can be coped with.

B. Children's anxiety has been enormously exaggerated.(夸大)

C. Children's anxiety can be eliminated(排除) with more parental care.

D. Anxiety, if properly controlled, may help children become mature.