Henry III didn't know much about biology. He went through six wives back in the 1500s, looking for one whocould bear him a son. Scientists now know that it's the father's sperm, not the mother's egg, which determines whether a baby is a boy or a girl. And last week researchers at the Genetics and IVF Institute, a private fertility(生育能力)center in Virginia, announced a new technique that will allow parents to choose the sex of their baby-to-be, before it has even been conceived. The scientist used a tiny laser detector to measure the DNA in millions of sperm cells as they pass single file through a narrow tube, like cattle being herded through a corral(牲口栏). In a study published last week, "girl sperm," which has more DNA—the genetic material— in each cell, was collected, while "boy sperm" was discarded. And when purified girl sperm was used to impregnate(使受孕)a group of mothers, 15 of 17 resulting babies turned out to be girls.

　　The researchers say that "sex selection" can also double a mother's chance of having a son and can be usedto avoid genetic diseases that affect only one gender, such as hemophilia(血友病). But some experts, like New York University fertility specialist Dr. Jamie Grifo, worry that sex selection could lead to a kind ofin uteri(子宫)discrimination, especially in cultures where sons are considered superior to daughters. "It's valuing one gender' over another," Grifo says. "I don't think that's something we should be doing." So far, patients at the institute have been asking for both boys and girls, in order to "balance" their families. And some ethics experts say that's fine, as long as parents are just looking for a little gender variety. "If you have three boys, and you want a girl," says University of Texas reproductive-law professor John Robertson, "that's not gender bias at all."

　　练习题：

　　Choose correct answers to the question:

　　1.The DNA in the sperm cells can be measured ______.

　　A.in the same way how the cattle are herded

　　B.when they pass through a tube one behind the other

　　C.after they pass through a laser tube

　　D.when they are scanned by a laser detector all at a time

　　2.The gender of the baby is decided by ______.

　　A.the father's DNA

　　B.the mother's DNA

　　C.the father's sperm

　　D.the mother's egg

　　3.According to this passage, the practice of "sex selection" ______.

　　A.can help to prevent all genetic problems

　　B.is totally unacceptable to ethics experts

　　C.was already realized five hundred years ago

　　D.will benefit families with certain inheritable diseases

　　4.Girl sperm was preferred to boy sperm in the research most probably because____

　　A.girl sperm contains more genetic material

　　B.more mother want to have girl babies

　　C.girl sperm is healthier and more active

　　D.girl sperm is more easily purified

　　5.It can be concluded from the passage that author’s toward”sex selection”is____

　　A.negative

　　B.positive

　　C.neutral

　　D.favorable