2. 外语
  3. We inherit our DNA from our parents. DNA is shuffled, recombined and【B1】______from one generation to another. Each individual on

We inherit our DNA from our parents. DNA is shuffled, recombined and【B1】______from one generation to another. Each individual on

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问题     We inherit our DNA from our parents. DNA is shuffled, recombined and【B1】______from one generation to another. Each individual on this earth received 23【B2】______of chromosomes from their parents(23 from dad and 23 from mom). Because DNA is【B3】______to a certain degree from one generation to the next, it is possible to【B4】______family lines by【B5】______specific markers.
    The【B6】______of the Earth are more closely related than what it is generally thought. Today there are 6【B7】______people living on this planet.  If we do some math, and we consider a generation to be about 25 years, 30 generations ago, every individual living today would have over 1 billion【B8】______ancestors. The estimated world population for the year 1250 AD was 400 million people.
    This means that the number of actual ancestors for each individual is smaller than the number of possible ancestors and【B9】______.These common ancestors were able to transmit specific markers【B10】______.
    The Molecular Genealogy Research Group is very interested in people with known genealogies【B11】______.Being 18 and older and having at least a four-generation pedigree chart are the only two qualifications in order to take part in this study.
【B7】
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答案billion
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大学英语四级

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