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Preimplantation Genetic Screening
Preimplantation genetic diagnosis (PGD or PIGD) is the genetic profiling of embryos prior to implantation (as a form of embryo profiling), and sometimes even of oocytes prior to fertilization. PGD is considered in a similar fashion to prenatal diagnosis. When used to screen for a specific genetic disease, its main advantage is that it avoids selective abortion, as the method makes it highly likely that the baby will be free of the disease under consideration. PGD thus is an adjunct to assisted reproductive technology, and requires in vitro fertilization (IVF) to obtain oocytes or embryos for evaluation. Embryos are generally obtained through blastomere or blastocyst biopsy. The latter technique has proved to be less deleterious for the embryo, therefore it is advisable to perform the biopsy around day 5 or 6 of development. The world's first PGD was performed by Handyside, Kontogianni and Winston at the Hammersmith Hospital in London. Female embryos were selectively transferred ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Preimplantation Genetic Diagnosis
Preimplantation genetic diagnosis (PGD or PIGD) is the genetic profiling of embryos prior to implantation (as a form of embryo profiling), and sometimes even of oocytes prior to fertilization. PGD is considered in a similar fashion to prenatal diagnosis. When used to screen for a specific genetic disease, its main advantage is that it avoids selective abortion, as the method makes it highly likely that the baby will be free of the disease under consideration. PGD thus is an adjunct to assisted reproductive technology, and requires in vitro fertilization (IVF) to obtain oocytes or embryos for evaluation. Embryos are generally obtained through blastomere or blastocyst biopsy. The latter technique has proved to be less deleterious for the embryo, therefore it is advisable to perform the biopsy around day 5 or 6 of development. The world's first PGD was performed by Handyside, Kontogianni and Winston at the Hammersmith Hospital in London. Female embryos were selectively transferred ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Robert Geoffrey Edwards
Sir Robert Geoffrey Edwards (27 September 1925 – 10 April 2013) was a British physiologist and pioneer in reproductive medicine, and in-vitro fertilisation (IVF) in particular. Along with obstetrician and gynaecologist Patrick Steptoe and nurse Jean Purdy, Edwards successfully pioneered conception through IVF, which led to the birth of Louise Brown on 1978. They founded the first IVF programme for infertile patients and trained other scientists in their techniques. Edwards was the founding editor-in-chief of ''Human Reproduction'' in 1986. In 2010, he was awarded the Nobel Prize in Physiology or Medicine "for the development of in vitro fertilization". Education and early career Edwards was born in Batley, Yorkshire, and attended Manchester Central High School on Whitworth Street in central Manchester, after which he served in the British Army, and then completed his undergraduate studies in biology, graduating with an Ordinary degree at Bangor University. He studied at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sex Selection
Sex selection is the attempt to control the sex of the offspring to achieve a desired sex. It can be accomplished in several ways, both pre- and post-implantation of an embryo, as well as at childbirth. It has been marketed under the title family balancing. According to the United Nations Population Fund, the reasons behind sex selection are due to three factors and provide an understanding for sex ratio imbalances as well as to project future trends. These factors are: # A preference for sons which stems from household structures "in which girls and women have a marginal social, economic and symbolic position, and consequently enjoy fewer rights." These household structures also focus on security in which sons are expected to provide support to their parents throughout their life; # Technological growth of prenatal diagnosis which allows parents to know the sex of their unborn child; and # Low fertility which increases the need for sex selection by reducing the probability of ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HLA Type
The human leukocyte antigen (HLA) system or complex is a complex of genes on chromosome 6 in humans which encode cell-surface proteins responsible for the regulation of the immune system. The HLA system is also known as the human version of the major histocompatibility complex (MHC) found in many animals. Mutations in HLA genes may be linked to autoimmune disease such as type I diabetes, and celiac disease. The HLA gene complex resides on a 3 Mbp stretch within chromosome 6, p-arm at 21.3. HLA genes are highly polymorphic, which means that they have many different alleles, allowing them to fine-tune the adaptive immune system. The proteins encoded by certain genes are also known as ''antigens'', as a result of their historic discovery as factors in organ transplants. HLAs corresponding to MHC class I ( A, B, and C), all of which are the HLA Class1 group, present peptides from inside the cell. For example, if the cell is infected by a virus, the HLA system brings fragment ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stillbirth
Stillbirth is typically defined as fetal death at or after 20 or 28 weeks of pregnancy, depending on the source. It results in a baby born without signs of life. A stillbirth can result in the feeling of guilt or grief in the mother. The term is in contrast to miscarriage, which is an early pregnancy loss, and Sudden Infant Death Syndrome, where the baby dies a short time after being born alive. Often the cause is unknown. Causes may include pregnancy complications such as pre-eclampsia and birth complications, problems with the placenta or umbilical cord, birth defects, infections such as malaria and syphilis, and poor health in the mother. Risk factors include a mother's age over 35, smoking, drug use, use of assisted reproductive technology, and first pregnancy. Stillbirth may be suspected when no fetal movement is felt. Confirmation is by ultrasound. Worldwide prevention of most stillbirths is possible with improved health systems. Around half of stillbirths occur durin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eugenics
Eugenics ( ; ) is a fringe set of beliefs and practices that aim to improve the genetic quality of a human population. Historically, eugenicists have attempted to alter human gene pools by excluding people and groups judged to be inferior or promoting those judged to be superior. In recent years, the term has seen a revival in bioethical discussions on the usage of new technologies such as CRISPR and genetic screening, with a heated debate on whether these technologies should be called eugenics or not. The concept predates the term; Plato suggested applying the principles of selective breeding to humans around 400 BC. Early advocates of eugenics in the 19th century regarded it as a way of improving groups of people. In contemporary usage, the term ''eugenics'' is closely associated with scientific racism. Modern bioethicists who advocate new eugenics characterize it as a way of enhancing individual traits, regardless of group membership. While eugenic principles have be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beta-thalassemia
Beta thalassemias (β thalassemias) are a group of inherited blood disorders. They are forms of thalassemia caused by reduced or absent synthesis of the beta chains of hemoglobin that result in variable outcomes ranging from severe anemia to clinically asymptomatic individuals. Global annual incidence is estimated at one in 100,000. Beta thalassemias occur due to malfunctions in the hemoglobin subunit beta or HBB. The severity of the disease depends on the nature of the mutation. HBB blockage over time leads to decreased beta-chain synthesis. The body's inability to construct new beta-chains leads to the underproduction of HbA (adult hemoglobin). Reductions in HbA available overall to fill the red blood cells in turn leads to microcytic anemia. Microcytic anemia ultimately develops in respect to inadequate HBB protein for sufficient red blood cell functioning. Due to this factor, the patient may require blood transfusions to make up for the blockage in the beta-chains. Repeate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Duchenne's Muscular Dystrophy
Duchenne muscular dystrophy (DMD) is a severe type of muscular dystrophy that primarily affects boys. Muscle weakness usually begins around the age of four, and worsens quickly. Muscle loss typically occurs first in the thighs and pelvis followed by the arms. This can result in trouble standing up. Most are unable to walk by the age of 12. Affected muscles may look larger due to increased fat content. Scoliosis is also common. Some may have intellectual disability. Females with a single copy of the defective gene may show mild symptoms. The disorder is X-linked recessive. About two thirds of cases are inherited from a person's mother, while one third of cases are due to a new mutation. It is caused by a mutation in the gene for the protein dystrophin. Dystrophin is important to maintain the muscle fiber's cell membrane. Genetic testing can often make the diagnosis at birth. Those affected also have a high level of creatine kinase in their blood. Although there is no known cu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tay–Sachs Disease
Tay–Sachs disease is a genetic disorder that results in the destruction of nerve cells in the brain and spinal cord. The most common form is infantile Tay–Sachs disease, which becomes apparent around three to six months of age, with the baby losing the ability to turn over, sit, or crawl. This is then followed by seizures, hearing loss, and inability to move, with death usually occurring by the age of three to five. Less commonly, the disease may occur in later childhood or adulthood (juvenile or late-onset). These forms tend to be less severe, but the juvenile form typically results in death by age 15. Tay–Sachs disease is caused by a genetic mutation in the ''HEXA'' gene on chromosome 15, which codes form a subunit of the hexosaminidase enzyme known as hexosaminidase A. It is inherited from a person's parents in an autosomal recessive manner. The mutation disrupts the activity of the enzyme, which results in the build-up of the molecule GM2 ganglioside within cells, lea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sickle-cell Anemia
Sickle cell disease (SCD) is a group of blood disorders typically inherited from a person's parents. The most common type is known as sickle cell anaemia. It results in an abnormality in the oxygen-carrying protein haemoglobin found in red blood cells. This leads to a rigid, sickle-like shape under certain circumstances. Problems in sickle cell disease typically begin around 5 to 6 months of age. A number of health problems may develop, such as attacks of pain (known as a sickle cell crisis), anemia, swelling in the hands and feet, bacterial infections and stroke. Long-term pain may develop as people get older. The average life expectancy in the developed world is 40 to 60 years. Sickle cell disease occurs when a person inherits two abnormal copies of the β-globin gene (''HBB'') that makes haemoglobin, one from each parent. This gene occurs in chromosome 11. Several subtypes exist, depending on the exact mutation in each haemoglobin gene. An attack can be set off by temp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biopsy
A biopsy is a medical test commonly performed by a surgeon, interventional radiologist, or an interventional cardiologist. The process involves extraction of sample cells or tissues for examination to determine the presence or extent of a disease. The tissue is then fixed, dehydrated, embedded, sectioned, stained and mounted before it is generally examined under a microscope by a pathologist; it may also be analyzed chemically. When an entire lump or suspicious area is removed, the procedure is called an excisional biopsy. An incisional biopsy or core biopsy samples a portion of the abnormal tissue without attempting to remove the entire lesion or tumor. When a sample of tissue or fluid is removed with a needle in such a way that cells are removed without preserving the histological architecture of the tissue cells, the procedure is called a needle aspiration biopsy. Biopsies are most commonly performed for insight into possible cancerous or inflammatory conditions. History T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X-linked
Sex linked describes the sex-specific patterns of inheritance and presentation when a gene mutation (allele) is present on a sex chromosome (allosome) rather than a non-sex chromosome (autosome). In humans, these are termed X-linked recessive, X-linked dominant and Y-linked. The inheritance and presentation of all three differ depending on the sex of both the parent and the child. This makes them characteristically different from autosomal dominance and recessiveness. There are many more X-linked conditions than Y-linked conditions, since humans have several times as many genes on the X chromosome than the Y chromosome. Only females are able to be carriers for X-linked conditions; males will always be affected by any X-linked condition, since they have no second X chromosome with a healthy copy of the gene. As such, X-linked recessive conditions affect males much more commonly than females. In X-linked recessive inheritance, a son born to a carrier mother and an unaffected fath ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
