试题与答案

科学工作者将一株矮杆低产的小麦与一株高杆高产的小麦进行杂交,在后代植侏中,出现了

题型:实验题

题目:

科学工作者将一株矮杆低产的小麦与一株高杆高产的小麦进行杂交,在后代植侏中,出现了矮杆低产、高杆高产、矮杆高产、高杆低产四种类型的小麦。请分析回答:

(1)人们应该选出其中哪种植株继续多代繁殖培育,从而得到有利于人类的新品种小麦?

             

(2)题中涉及到的小麦性状中,属于相对性状的有:               

(3)杂交亲代中的矮杆低产和高杆高产性状在后代中依然出现,这种与亲代相似的现象叫

          ,后代中出现了矮杆高产和高杆低产两种新类型,这种与亲代不同的现象叫做

          

答案:

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The iconic American family, with mom, dad and kids under one roof, is fading. In every state the numbers of unmarried couples, childless households and single-person households are growing faster than those comprised of married people with children, finds the 2010 census. And the trend has a potent class dimension. Traditional marriage has evolved from a near-universal ritual to a luxury for the educated and affluent.

There barely was a marriage gap in 1960: only four percentage points separated the wedded ways of college and high-school graduates(76% versus 72%). The gap has since widened to 16 percentage points, according to the Pew Research Centre.

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Americans with a high-school degree or less tell researchers they would like to marry, but do not believe they can afford it. Instead, they raise children out of wedlock. Only 6% of children born to college-educated mothers were born outside marriage, according to the National Marriage Project. That compares with 44% of babies born to mothers whose education ended with high school.

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