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Preimplantation Genetic Diagnosis- Screening for Genetic Diseases |
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Preimplantation genetic diagnosis for screening sex linked genetic diseases, identifying damaged chromosomes, and gender selection, has been in use in the United States for several years with excellent results. Review the history of PGD for a concise overview of how PGD came into widespread use. Preimplantation genetic diagnosis permits the screening of embryos for several specific genetic diseases in addition to gender selection for sex linked genetic diseases.
Not all genetic diseases can be screened but the list of those that can continues to grow.
Preimplantation genetic diagnosis, can help identify many genetic abnormalities before the embryo is transferred to the uterus. Genetic errors arise from deletions
or insertions of genetic material, abnormal numbers of
whole chromosomes or genes, and even from misplacement
of a single base in the DNA sequence. Genetic abnormalities
can range from relatively harmless to severe; from vitamin
deficiencies and food allergies to cancer, birth defects
and increased infant mortality.
PGD, and other significant advances
in technology, have enabled researchers to trace many
disorders and diseases to their roots in the genetic
code. Chromosome stretches, or even isolated genes,
can now be used as markers to identify individuals at
risk for certain illnesses.
Gender selection using PGD to screen for sex linked genetic diseases has become an effective procedure to diagnose many genetic diseases. Oftentimes, genetic abnormalities are not gender related and PGD can screen for damaged or translocated chromosomes, aneuploidy (abnormal number of chromosomes) and other defects The ability to recognize genetic
warning signs is rapidly becoming the most effective
tool for prevention, diagnosis, and treatment of genetically
based disorders. An estimated 60 percent of all naturally
occurring reproductive losses in pregnancies are associated
with chromosomal abnormalities in the embryo.
A normal embryo has 22 pairs of
chromosomes called autosomes and 1 pair of sex chromosomes
(XX or XY). Embryos that do not carry the normal pair
of each chromosome are called aneuploids. Those that
contain three copies of a particular chromosome (Trisomy)
are the cause of some genetic disorders such as Down's
syndrome (Trisomy 21). There are other less common trisomies of
chromosomes 13, 16, 18 and 22. Embryos that contain
only one copy of a chromosome (Monosomy) are by and
large nonviable.
PGD and genetic analysis can differentiate abnormal aneuploid embryos, either
with monosomy (one missing) or trisomy (an extra one),
which are usually normal in appearance. It is not possible
to distinguish these morphologically from other embryos.
Without preimplantation genetic diagnosis analysis, many of these
embryos are unknowingly transferred to patients.
HRC is one of the largest providers of assisted
reproductive treatments, including PGD, in the US.
Both the physicians and staff of HRC are committed to
maintaining the highest standard of infertility care in reproductive
medicine in terms of moral and ethical practices. Significant
experience in infertility treatment and embryo culture,
highly skilled medical and laboratory personnel make
it possible to offer PGD
technology to couples. Preimplantation genetic diagnosis to identify sex linked genetic diseases is offered to couples at risk of having a genetically
abnormal fetus. Screening for known genetic disorders can avoid the birth of
an affected child or having to face the painful decision
of a pregnancy termination.
Genetic Diseases that Can
be Screened Using Preimplantation Genetic Diagnosis
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Achondroplasia |
Cystic fibrosis |
Hypophosphatasia |
PKU |
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ADPKD1 |
Down syndrome |
Incontinentia pigmenti |
Retinitis pigmentosa |
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ADPKD2 |
Duchenne muscular dystophy |
Kell disease |
SCA6 oSickle cell anemia |
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Adrenoleukodystrophy |
Dystonia |
Klinefelter syndrome |
Sonic hedgehog mutations |
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Age-related aneuploidies |
Epidermolysis bullosa |
LCHAD |
Spinal muscular atrophy (SMA) |
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Alpha-1-antitrypsin |
Familial dysautonomia |
Lesch Nyhan syndrome |
Tay-Sachs disease |
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Alport disease |
Fanconi anemia |
Marfan syndrome |
Tuberous sclerosis |
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Amyloid precursor protein (APP)
mutation |
FAP |
Multiple epiphysial dysplasia |
Turner syndrome |
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ARPKD |
Fragile X syndrome |
Myotubular myopathy |
Von Hippel Lindau |
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Becker muscular dystrophy |
Gaucher disease |
NF1 and NF2 |
X-linked hydrocephaly |
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Beta-thalassemia |
Hemophilia A and B |
Norrie disease |
X-linked hyper IgM syndrome |
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Charcot Marie Tooth disease |
HLA genotyping |
Osteogenesis imperfecta |
1 |
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Chromosomal translocations |
HSNF5 mutation |
OTC deficiency |
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Congenital adrenal hyperplasia |
Huntington disease |
P53 mutations |
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As research continues, new diseases are constantly added to the list of conditions which can be diagnosed using PGD. |
