A Genitic Disorder is an illness caused by abnormalities in genes or chromosomes, especially a condition that is present from before birth. Most genetic disorders are quite rare and affect one person in every several thousands or millions.
A genetic disorder may or may not be a heritable disorder. Some genetic disorders are passed down from the parents' genes, but others are always or almost always caused by new mutations or changes to the DNA. In other cases, the same disease, such as some forms of cancer, may be caused by an inherited genetic condition in some people, by new mutations in other people, and by non-genetic causes in still other people.
Some types of ressicive gene disorders confer an advantage in certain environment when only one copy of the gene is present
This are the example of Genetic Disorder:
Down
syndrome or Down's syndrome, (also known as trisomy 21), is a
chromosomal conditiom caused by the presence of all or part of an extra
21st. chromosome It is named after John Langdon Down, the British
physician who described the syndrome in 1866. The condition was
clinically described earlier in the 19th century by Jean Etienne
Domonique Esquirol in 1838 and Edouard Seguin Down syndrome was
identified as a chromosome 21 trisomy by Dr. Jérôme Lejeune in 1959. Down syndrome in a fetus can be identified through chorrionic villus sampling or amniocentesis during pregnancy, or in a baby at birth. in 1844.
Down syndrome is a chromosomal condition characterized by the presence of an extra copy of genetic material on the 21st chromosome, either in whole (trisomytranslocations).
The effects and extent of the extra copy vary greatly among people,
depending on genetic history, and pure chance. The incidence of Down
syndrome is estimated at 1 per 733 births, although it is statistically
more common with older parents due to increased mutagenic exposures upon
some older parents' reproductive cells. Other factors may also play a
role. Down syndrome occurs in all human populations, and analogous
conditions have been found in other species such as chimpanzees and mice. 21) or part (such as due to
Often Down syndrome is associated with some impairment of cognitive ability and physical growth,
and a particular set of facial characteristics. Individuals with Down
syndrome usually have low intelligence, such as to constitute mild to
moderate intellectual disability. Many children with Down syndrome who
have received family support, enrichment therapies and tutoring manage
to graduate from high school and college, and are able to do paid work.
The average IQ of children with Down syndrome is around 50, compared to normal children with an IQ of 100. A small number have a severe to high degree of intellectual disability.
Angelman syndrome (AS) is a neuro-genitic disorder
characterized by intellectual and developmental delay, sleep
disturbance, seizures, jerky movements (especially hand-flapping),
frequent laughter or smiling, and usually a happy demeanor.
AS
is a classic example of genomic imprinting in that it is usually caused
by deletion or inactivation of genes on the maternally inherited
chromosome 15 while the paternal copy, which may be of normal sequence,
is imprinted and therefore silenced. The sister syndrome, Prade-Willi
Syndrome, is caused by a similar loss of paternally inherited genes and
maternal imprinting. AS is named after a British pediatrician, Dr. Harry Angelman, who first described the syndrome in 1965. An older, alternative term for AS, happy puppet syndrome, is generally considered pejorative
and stigmatizing so it is no longer the accepted term, though it is
sometimes still used as an informal term of diagnosis. People with AS
are sometimes known as "angels", both because of the syndrome's name and
because of their youthful, happy appearance.
Klinefelter syndrome, 47, XXY, or XXY syndrome
is a condition in which human males have an extra X chromosome. While
females have an XX chromosomal makeup, and males an XY, affected
individuals have at least two X chromosome and at least one Y chromosome. Because of the extra choromosome, individuals with the condition are usually referred to as "XXY Males", or "47, XXY Males".
Klinefelter's syndrome is the symptoms of the disease Seminiferous Tuble Dysgenesis
As stated below this form of hypogonadism was first described by
Klinefelter et al in 1942. The account given by Klinefelter came to be
known as Klinefelter's syndrome as his name appeared first on the
published paper, and Seminiferous Tubule Dysgenesis was no longer used.
Prader–Willi syndrome (abbreviated PWS)
is a rare genetic disorder in which seven genes (or some subset
thereof) on chromosome 15 (q 11-13) are deleted or unexpressed
(chromosome 15q partial deletion) on the paternal chromosome. It was
first described in 1956 by Andrea Prader (1919–2001), Heinrich Willi
(1900–1971), Alexis Labhart (1916), Andrew Ziegler, and Guido Fanconi of
Switzerland.
Characteristic of PWS is "low muscle tone, short stature, incomplete
sexual development, cognitive disabilities, problem behaviors, and a
chronic feeling of hunger that can lead to excessive eating and
life-threatening obesity."
The incidence of PWS is between 1 in 25,000 and 1 in 10,000 live
births. The paternal origin of the genetic material that is affected in
the syndrome is important because the particular region of chromosome 15
involved is subject to parent of origin imprinting,
meaning that for a number of genes in this region only one copy of the
gene is expressed while the other is silenced through imprinting. For
the genes affected in PWS, it is the paternal copy that is usually
expressed, while the maternal copy is silenced. This means that while
most people have a single working copy of these genes, people with PWS
have a non-working copy and a silenced copy. PWS has the sister syndrome
Angelman Syndrome in which maternally derived genetic material is
affected in the same genetic region.
Turner syndrome or Ullrich-Turner syndrome (also known as "Gonadal dysgenesis":550),
45 XO, encompasses several conditions in human females, of which
monosomy X (absence of an entire sex chromosome, the Barr Body) is most
common. It is a chromosomal abnormality in which all or part of one of
the sex chromosomes
is absent (unaffected humans have 46 chromosomes, of which two are sex
chromosomes). Normal females have two X chromosomes, but in Turner
syndrome, one of those sex chromosomes is missing or has other
abnormalities. In some cases, the chromosome is missing in some cells
but not others, a condition referred to as mosaicism or 'Turner mosaicism'.
Occurring in 1 in 2000 – 1 in 5000 phenotypic females, the
syndrome manifests itself in a number of ways. There are characteristic
physical abnormalities, such as short stature, swelling, broad chest,
low hairline, low set ears, and webbd necks.Girls
with Turner syndrome typically experience gonadal dysfunction
(non-working ovaries), which results in amenorrhea (absence of menstrual
cycle) and sterility. Concurrent health concerns are also frequently
present, including congenital heart disease, hypothyroidism (reduced
hormone secretion by the thyroid), diabetes, vision problems, hearing
concerns, and many autoimmune diseases. Finally, a specific pattern of cognitive deficits is often observed,
with particular difficulties in visuospatial, mathematical, and memory areas.
