Scientists Map Entire DNA of Human Fetus

December 10, 2010

Courtesy: foxnews.com

Parents may soon be able to find out if their unborn child is prone to any inherited diseases, researchers said on Thursday, after developing a non-invasive technique to draw the entire gene map of the human fetus.

By analyzing a sample of the mother’s blood, which contains DNA from the fetus, scientists in Hong Kong and the United States were able to identify all the DNA strands that belong to the child and piece them together.

“Before this work, people only could look for one disease at one time but now you can construct a screen for a number of diseases which are prevalent in any particular population,” said lead author Dennis Lo, professor of medicine from the Chinese University in Hong Kong.

The research team’s breakthrough was discovering that the mother’s plasma holds the entire fetal genome. Previously, only part of the baby’s DNA was thought to be in the mother’s blood.

“Now that we know (the) entire fetal genome is in there, you can look for any disease that is genetically inherited.”

The study, published in the journal Science Translational Medicine on Thursday, recruited a couple undergoing prenatal diagnosis for a hereditary blood disorder, beta-thalassemia.
“In the mother’s blood, 90 percent of the DNA is her own … and 10 percent is the baby’s. Half of the fetal genome is from father and half from mother,” Lo said.

Lo described the process as akin to putting together a jigsaw puzzle with millions of pieces — only in this case, 10 times as many pieces from a much larger jigsaw were mixed in with it too.

“The whole genome is fragmented into millions of pieces and by this exercise, we assemble it back,” Lo said.
“It’s like assembling a jigsaw puzzle with millions of pieces. But to make it more challenging, you mix in 10 times (the number of pieces) from another jigsaw puzzle, that’s the mother’s own DNA. And you are trying to assemble the child’s.”

Experts who were not involved in the study called for caution.

“It is too early to apply the technology widely as we are not yet able to interpret many of the results that can be generated accurately,” said Christine Patch, chair of the British Society for Human Genetics. “We do not randomly test pregnancies for a long list of … conditions that may only manifest in adult life on the basis that individuals may not want to know that information when they are older.”


Chinese Study Suggests New Way to Test for Genetic Diseases

December 10, 2010

Courtesy: health.usnews.com

A new test that requires only a tiny sample of a mother’s blood to scan the genome of a fetus may offer a safer alternative to current methods of prenatal screening for genetic diseases, a new study suggests.

Currently, a sample of fetal tissue is collected using invasive procedures such as amniocentesis or chorionic villus sampling, both of which pose a small but definite risk to the fetus.

But, Chinese researchers found that fetal DNA floating in the mother’s blood contains the entire fetal genome and can reveal a number of genetic and chromosomal disorders in the fetus.

They used the method on a couple undergoing prenatal diagnosis for a type of genetic anemia called beta-thalassemia. The results showed that the fetus had inherited the beta-thalassemia mutation from the father and a normal gene from the mother, meaning the fetus was a carrier of the disease.

The study is published in the Dec. 8 issue of Science Translational Medicine.


Couples urged to follow doctors’ pre-marital advice

December 24, 2009

Courtesy by: gulf-times.com
Those who intend to get married should follow their doctor’s instructions to avoid health problems, Pre-marital Screening Committee chairman Dr Ahmed Kamal Naji has said.

“This should be coupled with a sound diet system, physical exercise, observing weight, giving up smoking, decreasing intake of stimulants like tea, coffee, carbonated drinks and sugars for their negative effect on fertility and fetus growth,” he explained.

Dr Naji said couples should never take any medicines without consulting their doctors.
“Women should take folic acid before pregnancy to minimise any deformation to the fetal nervous tube. For women with some types of heart diseases, the case has to be stable before pregnancy for the sake of the mother’s life,” he advised.

He added that during pregnancy, the mother should have appropriate treatment which does not affect the foetus, especially medicines taken for thyroid gland, epilepsy, blood clotting, blood pressure and diabetes. “All these are necessary to avoid any hard and lengthy trouble in the future,” he stressed.

The national pre-marital check-up and counselling programme, which was launched recently, screens would-be couples for potential inherited infections or diseases they could give to their babies, especially in close-blood marriages.

Family marriages play a great role in the infection of inherited diseases caused by recessive inheritance, such as the sickle cell anemia and thalassemia.

Dr Naji said according to the type of the disease, avoidance possibilities can be discussed.

However, he said screening did not include tests that check fertility of any of the couples.

A statement issued recently by the pre-marital screening committee has emphasised that it did not mean that marriages outside the family will guarantee that babies will be free of inherited diseases or even recessive inherited diseases.

“That is why it is important to conduct certain tests to determine if the person is carrying the disease.

Therefore, pre-marital screening is important for relative and non-relative couples,” it says.

The statement explains that the potential infection of congenital diseases among couples of family relationships is higher.

“The closer the relation, the higher is the infection as every individual, regardless of age or health condition, has about 5 -10 defective genes which do not cause any disease for the person carrying them, as he possesses similar genes that are disinfected.”

“When the couple carrying infected genes get married, their children might receive double dose of those genes, that is to say, each of the father and mother gives infected genes. This causes health problems according to the type of the infected gene.”

The Supreme Council of Health has divided the diseases to be screened for into two categories: contagious and inherited diseases.

The purpose of including contagious diseases such as hepatitis B and C, and HIV/Aids is to avoid some of them through treatment or vaccination, or else to warn the other party against potential infection.

Other tests in the premarital screening includes haemoglobin abnormalities (thalassemia and sickle cell anemia), hemophilia (A and B) and syphilis.

“Many of the inherited diseases have no cure, some are difficult to treat and their treatment might be very costly and might require some advice or counselling in addition to other lengthy procedures,” Dr Naji said.

He added that premarital screening has become an appropriate, effective and less expensive tool to combat and prevent inherited diseases, adding that it implied great benefits for the whole society as it protects against inherited diseases which cost much to be cured or treated.


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