Once they decided to have children, MiShel and Carl Meissner tackled the next big issue: Should they try to have a girl It was no small matter. MiShel"s brother had become blind from a hereditary condition in his early 20s, and the Meissners had learned that the condition is a 11 passed from mothers to sons. If they had a boy, he would have a 50 per cent chance of having the condition. A girl would be 12 .
The British couple"s inquiries about gender selection led them in 1999 to Virginia, US where a new sperm (精子)-separation technique, called MicroSoft, was under 13 . When MiShel became pregnant, she gave birth to a daughter. They will try to have a second daughter using the technique later this year.
The technique separates sperm into two groups—those that carry the X-chromosome (producing a female baby) and those that carry the Y-chromosome (producing a male baby). The technology was developed in 1990s, but last month"s opening of a laboratory in California 14 the company"s first expansion.
"We believe the number of people who want this technology is greater than those who have 15 to it," said Keith L. Blauer, the company"s clinical director.
This is not only a 16 effective way to select a child"s gender. It also brings a host of ethical (伦理的) and practical considerations—especially for the majority of families who use the technique for 17 reasons.
The clinic offers selection for two purposes to help couples avoid passing on a gender4inked 18 disease and to allow those who already have a child to "balance" their family by having a baby of the opposite .
The technology is still 19 . However, Blauer says the company has an impressive success rate: 91 per cent of the women who become pregnant after sorting for a girl are successful, while 76 per cent who sort for a boy and get pregnant are successful.
The technique separates sperm based on the fact that the X-chromosome is larger than the Y-chromosome. A machine is used to 20 the size differences and sort the sperm accordingly. The result is then checked using another type of DNA ysis to ensure that it contains mostly X-or Y-bearing sperm. The desired sample is then used for artificial insemination (授精) or test tube fertilization.
A. genetic B. overlapped C. marked D. unaffected
E. perpetually F. investigation G. access H. feat
I. disorder J. gropes K. experimental L. seemingly
M. elicit N. nonmedical O. distinguish