Karyotyping
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Abortus Material: |
Abortus material is tested
for the people who had the cases of previous Abortions,
known paternal chromosomal abnormalities, previous deliveries
of children with chromosomal abnormalities.
The cytogenetic analyses (Karyotyping) of the abortus
material provide important information about the recurrence
risks and possible management for the couples with recurrent
spontanous abortions. The methods of cytogenetic analyses
depend on primarily cell culture that has relatively
higher (10- 40%) failure. The most common chromosomal
abnormalities in abortus materials are numerical chromosomal
abnormalities.
More than 50% of spontaneous abortions have chromosomal
abnormalities including primarily numerical abnormalities
such as autosomal trisomies (29%), monosomy X (10%),
polyploidy (10%) and mosaicism or structural chromosomal
abnormalities (2%). The cytogenetic analyses of the
abortus material provide valuable information about
the recurrence risks and possible therapies for the
couples with recurrent spontaneous abortions. The cytogenetic
detections depend on providing viable tissue to perform
primary culture and harvest metaphase chromosomes. The
methods of the cell culture and chromosomal analyses
are well described and accepted as a diagnostic method
for last four decades. It is well known that these applications
had some limitations such as relatively higher (10-40%)
tissue culture failure and providing karyotypes not
presenting concepts due to selective overproduction
of maternal cells.
Amniotic Fluid:
Amniotic fluid is analyzed when the maternal age > 35
years, previous abortions or missed abortions, paternal
chromosomal structural abnormalities, malformation,
diagnostic findings (PAPP-A, Trple test), abnormal ultrasound,
previous delivery of children with chromosomal abnormalities,
previous delivery of children with malformation, mutagenic
exposure during pregnancy.
Karyotyping looks at cells under a microscope to study
the size, shape, and number of chromosomes, which are
the thin strands in the center (nucleus) of most of
the cells in the body. A person normally has 46 chromosomes.
The chromosomes carry genetic information that determines
a person's inherited features, such as sex, eye color,
and blood type. Each chromosome is made up of many sections
called genes. Extra or missing pieces of a chromosome
can cause problems with a person's development and growth
and with any of the body's functions.
Karyotyping can be done on most other cells in the body,
but usually it is done on white blood cells (lymphocytes).
It also can be done on cells taken from a tissue sample
(such as skin or bone marrow), from amniotic fluid,
or from chorionic villi sampling (CVS).
To test amniotic fluid, an amniocentesis is performed.
Testing on placental tissue is done after chorionic
villous sampling or after a miscarriage.
Ataxia Telengiectasia:
Ataxia-telangiectasia is a rare, childhood neurological
disorder that causes degeneration in the part of the
brain that controls motor movements and speech. Its
most unusual symptom is an acute sensitivity to ionizing
radiation, such as X-rays or gamma-rays. The first signs
of the disease, which include delayed development of
motor skills, poor balance, and slurred speech, usually
occur during the first decade of life. Telangiectasias
(tiny, red "spider" veins), which appear in
the corners of the eyes or on the surface of the ears
and cheeks, are characteristic of the disease, but are
not always present and generally do not appear in the
first years of life. About 20% of those with A-T develop
cancer, most frequently acute lymphocytic leukemia or
lymphoma. Many individuals with A-T have a weakened
immune system, making them susceptible to recurrent
respiratory infections. Other features of the disease
may include mild diabetes mellitus, premature graying
of the hair, difficulty swallowing, and delayed physical
and sexual development. Children with A-T usually have
normal or above normal intelligence.
Blood Karyotyping can be done on the people showing
symptoms of abnormal co-ordination of limbs becomes(peripheral
ataxia), slurred speech, eye movements, lower intellect,
immune problems.
Blood Chromosomes:
Karyotyping is a standard arrangement of photographic
or computer-generated images of chromosome pairs from
a cell in ascending numerical order, from largest to
smallest. Chromosome abnormalities can be numerical,
as in the presence of extra or missing chromosomes,
or structural, as in translocations, inversions, large-scale
deletions or duplications. Numerical abnormalities,
also known as aneuploidy, often occur as a result of
nondisjunction during meiosis in the formation of a
gamete; trisomies, in which three copies of a chromosome
are present instead of the usual two, are common numerical
abnormalities. Structural abnormalities often arise
from errors in homologous recombination. Both types
of abnormalities can occur in gametes and therefore
will be present in all cells of an affected person's
body, or they can occur during mitosis and give rise
to a genetic mosaic individual who has some normal and
some abnormal cells.
Chromosome analysis is an important component in the
diagnosis and evaluation of genetic disorders. Chromosome
abnormalities in which there is too much or too little
genetic material can result in congenital malformations,
mental retardation, or aberrant sexual differentiation.
Chromosome disorders occur in approximately 1 in 150
liveborns and are a significant cause of mental retardation
and dysmorphic features. In addition, over 50% of first
trimester spontaneous abortions are due to a fetal chromosome
abnormality.
Karyotyping is used to detect infertility, deliver of
children with chromosomal abnormalities, recurrent abortions,
abnormal findings in prenatal chromosomal analysis,
suspicion of Dysmorphic Syndrome, Suspicion of gonosomal
abnormalities.
Bone Marrow Chromosome:
Chromosome analysis is indicated for individuals with
particular leukemias and hematologic disorders. A chromosome
analysis on bone marrow or leukemic blood may be helpful
in defining the specific form of leukemia and/or may
aid in providing prognostic information. In patients
who have had a bone marrow transplant,Leukemia and hematological
disorders, chromosome analysis may be useful in monitoring
engraftment or hematological disorders.
Chorionic Villi Samples (Long
term culture):
Chorionic villus sampling (CVS), also known as chorionic
villus biopsy, is a prenatal test that can detect genetic
and chromosomal abnormalities of an unborn baby.
Chorionic villus sampling is best performed between
10 and 12 weeks of pregnancy. The procedure is performed
either through the vagina and the cervix (transcervically)
or through the abdomen (transabdominally) depending
upon the preferences of the patient or the doctor. In
some cases, the location of the placenta dictates which
method the doctor uses. Both methods are equally safe
and effective. Following the preparation time, both
procedures take only about five minutes. Women undergoing
chorionic villus sampling may experience no pain at
all or feel cramping or pinching. Occasionally, a second
sampling procedure must be performed if insufficient
villus material was obtained.
Cord blood Prenatal- (chromosome):
Prenatal diagnosis employs a variety of techniques to
determine the health and condition of an unborn fetus.
Without knowledge gained by prenatal diagnosis, there
could be an untoward outcome for the fetus or the mother
or both. Congenital anomalies account for 20 to 25%
of perinatal deaths. Specifically, prenatal diagnosis
is helpful for:
• Managing
the remaining weeks of the pregnancy
• Determining
the outcome of the pregnancy
• Planning for
possible complications with the birth process
•
Planning for problems that may occur in the newborn
infant
• Deciding whether to continue the
pregnancy
• Finding conditions that may affect
future pregnancies
Falconi’s
Anemia (Mitomycin Assay):
Fanconi anemia is a blood disorder characterized by
pancytopenia (deficiency of red blood cells, white blood
cells and platelets), increased risk for cancer, and
congenital birth defects. The disease is highly variable
and is frequently associated with cardiac, kidney and
limb abnormalities. Short stature is commonly observed
in children and adults with Fanconi anemia, and other
growth measurements may also be below normal. Bleeding
episodes and bruising are common, as are hormonal problems
and infertility. The majority of individuals with Fanconi
anemia are diagnosed during childhood, but many do not
survive beyond young adulthood. This is frequently a
result of leukemia or other cancers, which are due to
bone marrow failure.
Cytogenetic analysis is used to reveal chromosome breakage,
which is characteristic of Fanconi anemia. Recently
the carrier of Fanconi anemia can be identified after
the gene for Fanconi anemia was isolated on chromosome
9.
Fibroblast culture for other test:
In children or adults with skin disorders like inherited
ichthyosis/epidermal bullosa, or enzyme defects, a skin
biospy is needed for an accurate diagnosis. Some metabolic
diseases or chromosomal disorders also require skin
fibroblast culture for accurate analysis. This is performed
on OPD basis.
Fragile X Syndrome-
Thymidine:
Fragile X is a family of genetic conditions, which can
impact individuals and families in various ways. These
genetic conditions are related in that they are all
caused by gene changes in the same gene, called the
FMR1 gene.
Fragile X syndrome (FXS) is the most common cause of
inherited mental impairment. This impairment can range
from learning disabilities to more severe cognitive
or intellectual disabilities. (Sometimes referred to
as mental retardation.) FXS is the most common known
cause of autism or "autistic-like" behaviors.
Symptoms also can include characteristic physical and
behavioral features and delays in speech and language
development.
Fragile X-associated tremor/ataxia syndrome (FXTAS)
is a condition which affects balance, tremor and memory
in some older male gene carriers.
Fragile X-associated primary ovarian insufficiency (FXPOI)
is a problem with ovarian function which can lead to
infertility and early menopause in some female gene
carriers.
Some gene carriers do not exhibit any of these features.
Fragile X can be passed on in a family by individuals
who have no apparent signs of this genetic condition.
In some families a number of family members appear to
be affected, whereas in other families a newly diagnosed
individual may be the first family member to exhibit
symptoms.
Prader willi
Syndrome- microdeletion chrom 15:
Prader-Willi syndrome (abbreviated
PWS) is a very rare genetic disorder, in which
seven genes (or some subset thereof) on chromosome 15
are missing or unexpressed (chromosome 15q partial deletion)
on the paternal chromosome.
Prader-Willi syndrome is also frequently associated
with an extreme and insatiable appetite, often resulting
in morbid obesity. There is currently no consensus as
to the cause for this particular symptom, although genetic
abnormalities in chromosome 15 disrupt the normal functioning
of the hypothalamus. Given that the hypothalamus regulates
many basic processes, including appetite, there may
well be a link. However, no organic defect of the hypothalamus
has been discovered on post mortem investigation.
Newborn with muscular hypotonia, children with obesity,
mental retardation, short stature, hygonadotropic hypogonadism
are tested for the syndrome by using cytogenetic analysis..
Recurrent Abortion
(husband and wife):
Spontaneous abortion occurs in 12 to 15 percent of all
pregnancies. A subset of patients habitually abort in
the first or second trimester. Studies have shown that
the risk of recurrent spontaneous abortion is much higher
in this subset. Family physicians are likely to encounter
the problem of recurrent spontaneous abortion and must
address both the medical and psychosocial implications.
This article reviews the literature and offers an approach
to the management of patients with recurrent spontaneous
abortion.
The most common cause of sporadic spontaneous abortion
is a chromosomal abnormality of the fetus. More than
60 percent of first-trimester fetal losses show some
type of cytogenetic abnormality. The most common abnormality
is aneuploidy (an abnormal chromosomal composition),
with autosomal trisomy accounting for more than 50 percent
of chromosomally abnormal abortuses. Other common types
of aneuploidy include XO, XXX, XXY and XYY. Polyploidy
accounts for approximately 22 percent of chromosomally
abnormal abortuses. Triploidy (3n = 69 chromosomes)
is approximately three times more common than tetraploidy
(4n = 92 chromosomes).
People suffering from infertility, delivery of children
with chromosomal abnormalities, recurrent abortions,
abnormal findings in prenatal chromosomal analysis,
suspicion of Dysmorphic Syndrome, Suspicion of gonosomal
abnormalities are advised to analyze their chromosomes..
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