Lifewatch: New embryo genetic test

Reported by Claire Hosmann - bio|email
Posted by Debra Worley - email

(WECT) - Fertility doctors have been screening embryos for genetic disorders for several years, but the number and type of diseases they can test for has been limited.

With a new genetic test, doctors can screen for thousands of traits all at once.

Mary Johnson is the mother of a health 3-year-old, with no history of fertility problems.  Now, she and her husband want another baby and are trying out a new gene chip test to make sure it will also be healthy.

At just eight cells, embryos can be screened using chips called microarrays.  Each chip is layered with DNA fragments.  They're scanned for thousands of specific genetic defects all at once.

"We try to hone in on the most common disorders that we see in healthy couples," said Dr. Jeffery Steinberg.

Dr. Steinberg said the test looks for genetic causes of down's syndrome and the risks of prostate, breast, and colon cancers, but experts caution DNA doesn't determine everything.

"If you do a DNA test on someone to predict their risk of heart disease, you're really only looking at a part of the picture," said Associate Director of Epidemiology Marta Gwinn, PhD.  "You're really only looking at what they came with, the hand they were dealt."

At 39, Mary and her 55-year-old Roy know age is a risk factor, but they also want to avoid passing along a family history of cancer and heart disease.

At about $20,000 a couple, this test isn't for everybody, but for Mary and Roy if it means the chance of a healthy sibling for 3-year-old Ava, it's worth it.

While it's possible to test for some adult-onset diseases in addition to eye color, Dr. Steinberg said it's best to test couples who have a known family disorder that's genetic or someone with a history of miscarriage.

For more information, please contact:
The Fertility Institutes
Encino, CA
(818) 728-4600

BACKGROUND: Genetic testing may be performed for a variety of reasons. The most common includes screening embryos for disease, checking to see if an unborn baby has a genetic disease, testing adults for genetic diseases before symptoms show, to find out whether a person carries a gene for a hereditary disease that may pass on to their children, or to confirm a diagnosis in a person who is showing signs or symptoms of a disease. All of this can be done by using a DNA sample taken from a person's blood, body fluids or tissues. Genetic tests look for alterations in a person's genes or changes in the level of key proteins coded for by specific genes. Abnormal results may mean that individual has inherited a disorder.

HOW IT WORKS: Every cell of the body has a full set of chromosomes and identical genes, with few exceptions. Microarrays are a new technique that allows a large number of different genetic sequences to be arranged on a slide so they can then be used to indentify specific sequences in an unknown mix of either DNA or RNA. When the genetic sequences are laid out on a slide, each piece of DNA is placed in an orderly arrangement. Microarrays may be used to examine gene expression within a single sample or to compare gene expression in two different cell types or tissue samples, such as to compare healthy and diseased tissue. The use of microarrays may also speed the identification of genes involved in the development of various diseases by enabling scientists to examine a much larger number of genes. The microarray actually characterizes the nature of the gene and the nature of the defect. The codes are examined on the genes and any errors in the genes code are displayed.

CONTROVERSIAL?  Some experts say this form of genetic testing allows parents to "design" children. Other experts condemn similar tests that allow parents to select the gender of their unborn child. A study and ethics opinion by the American College of Obstetricians and Gynecologists condemned all indications of elective gender selection as devaluing women and sexist. Researchers looked into this further by investigating gender tendencies among couples who underwent IVF in 2006. They found Chinese, Arab/Muslim and Asian-Indian couples most often selected males. Other ethnicities actually seemed to prefer selecting a female.

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