Creating Perfect babies
IVF and Genetic Screening
The idea of screening embryos before pregnancy is not a new one. As early as 1967 Edwards (the pioneer of Human IVF) and Gardner reported the sexing of rabbit embryos. It was suggested in that article that a similar approach could be used to avoid genetic disease in humans one day.
The refinements of these IVF techniques, the increased use of micromanipulation together with the rapid progress in molecular genetics makes screening and transfer of embryos possible.
Pre-implantation genetic Diagnosis (PGD) is the detection of genetic defects or disease in embryos derived from In Vitro fertilization (IVF) after which the unaffected embryos are transferred into the uterus. The aim of PGD as a form of early prenatal diagnosis is avoidance through selection of embryos. In this way a couple at risk of having a child with a genetic disorder can initiate a pregnancy knowing that the child is not affected.
PGD aims to eliminate the risk for genetically disadvantaged couples, eliminate the period of time for prenatal diagnosis and subsequent psychological trauma the couple may face with the decision of a selective abortion.
PGD may be a solution to couples unwilling to undergo voluntary abortion for ethical or religious reasons.
The law in Greece allows sex selection only for sex-linked hereditary diseases.
FISH, PGD and Pre-implantation Genetic Screening.
An alternative method for detecting sex-linked diseases (genetic diseases only affecting one of the sexes) involved the use of fluorescent chromosome dyes to detect the Y and the X chromosome
The dyes of different colours could, in a cell biopsied from an embryo, simultaneous detect the two chromosomes (X, Y).
After improvements to this technique (FISH-fluorescent in situ hybridization), it was possible to examine more chromosomes simultaneously and quicker.
While PGD is offered to couples at risk of transmitting genetic disease this is not the case for Pre-implantation Genetic Screening (PGS).
The objective of PGS is to increase the chance of pregnancy after IVF, and reduce abortion by selecting the healthiest embryos.
Screening for aneuploidy (abnormal numbers of chromosomes) by multi colour FISH may be a future selection criteria, other than morphology and development status.
This screening of embryos has caused much debate and has been likened to eugenics (selection for best characters in the human race): designer babies "will be ordered" rather than conceived naturally, it is argued.
But this is simple not possible. Many human characteristics are not the result of one gene and a subtle interplay of many genes may be involved.
If a certain desired human characteristic were rare (and human nature dictates this) the number of embryos to be screened to find the desired combination would be enormous!!!!
To have a child with a desired characteristic, the best chance is the time honoured, traditional way of finding a mate with those characteristics.
There is a distinction between disease prevention practiced by caring parents and that, which was practiced in the early 20th century in the name of eugenics.
Care must be taken to explain the difference between stopping disease (science now) and enhancing genes (science fiction).
What is cloning?
Cloning is the construction of a cell or cells containing the DNA from one individual, bypassing the process of reproduction.
This occurs in nature with bacteria and higher organism (some species of snails, shrimp and amphibians).
Identical twins like clones have exactly the same genetic make-up, because they are derived from the same sperm and same oocyte.
The fertilized oocyte splits into two identical embryos, therefore having the same genetic material and sharing the same womb, being born simultaneously.
(Non-identical twins arise when two oocyte are released at ovulation instead of the usual one and are fertilised by two different spermatozoa).
How do we make clones?
The most common way is by "Nuclear Transfer" whereby the nuclear material of a cell (the DNA) is taken from one cell and placed in an oocyte that has had its own nucleus removed. Afterwards the fusion is completed by electric or chemical means.
Why was dolly so special?
It was the first mammal that was cloned from DNA from an adult animal. Earlier clones had been created from using cells from embryos (that have the ability to form other cells).
Importantly, cloning proved that cells can be re-programmed to form other cell types-which was previously believed only existed in some embryonic cells.
What made Dolly the sheep different was that she was cloned from an udder cell of an adult sheep.
What are the dangers of cloning?
Warnings have been voiced from the very scientist that created the first clones.
The percentage of "constructed animals" that develop to birth is about 1%.
A great number of these have presented pulmonary, circularly and immune problems.
Fears-advantages-future
When the first successful organs transplants were announced outcries of new Frankensteins were to be heard.
Must we always look at new medical innovations as something bad?
The birth of Dolly proved a new found adaptability of the cell to return to its earliest developmental stage and means that maybe cells of one type can be re-programmed to form other types of cells. This would indeed be very important for many medical conditions.
Stem cells
When we talk about embryo research we usually confuse and refer to a specific type of cell called a Stem Cell.
These cells, like the cells used in cloning, can be re-programmed to form embryos. They can alter their "developmental fate" to become almost any other cell type in the body.
One concerns is from where these cells originate:
Although some types of stem cell are found in the adult body in very small quantities the majority (and the most useful type) are derived from an early stage of the embryo (the blastocyst).
The cells from the inner cell mass of these embryos under special culture conditions have the ability to form other types, making them very important for not only cloning but in transplantation and in the future, organ and tissue regeneration.
Therapeutic Cloning
If tissue can be regenerated, this could help people with Parkinson's, Alzheimer's and even diabetes. Also if it is possible to recreate nerve cells we may help sufferers of limb damage and spinal injury.
Modern genetic engineering may be hit and miss but far more effective.
A thorough bred horse or breed of dog can be considered a product of genetic manipulation. The process however took many generations to achieve its desired effect.
As opposed to the "guinea pigs", cell lines and tissue cultures created and selected in the laboratory are cheaper, quicker and more ethical in reaching a desired end.
Can cloning be used to bring back dinosaurs?
The success of cloning is still too low but not impossible-tissue samples of the wholly mammoth have been found frozen for thousands of years.
Interestingly, for several years now, before the popularity of the book "Jurassic Park" The London Zoo has operated a "Frozen Zoo". Animals faced with extinction have their embryos frozen. A female from a related species can be used in the future as a Surrogate.
