DNA is a long chain of molecule that is made up of pairs of ordered building blocks. Bases have such blocks as
adenine (A), Guanine (G), cytosine (C), and thymine (T). DNA is present in nearly all cells of a living body in the form
of chromosome that has DNA thickly wound.
All genetic information of a human (genome) consist of DNA (deoxyribonucleic acid), and analyzing nucleic acid
sequence comes up with desired genetic information.
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Genetic Hearing Loss
Hereditary hearing loss, which shows in about 50% of congenital
hearing loss, is caused by functional abnormalities with genes,
and occurs from a person's inheritance of his or her parents' genes.
70% of hereditary hearing loss occurs as nonsyndromic deafness, which
shows an independent instance of sensorineural hearing loss without
involving abnormalities with other organs. Nonsynromic deafness
registers severer hearing loss compared to other genetic types of
hearing loss, and as it shows only hearing loss without involving
abnormalities with other organs, it is hard to track its cause.
Therefore, it is important to identify its accurate cause and mutation
precisely through a test for hereditary hearing loss
How many babies are born with hearing loss ? Because of
Congenital severe hearing loss occurs with about 1 to 5 out
of every 1,000 newborns. This ratio suggests that it is a
commonplace disease, when compared to disorders with other
sensory organs such as vision, touch, taste, and smell. Its
prevalence is high, even when compared to inherited metabolic
disorders for which a postnatal test is currently required.
* Phenylketonuria with 3 to 10 persons out of every 100,000 people and hypothyroidism with 28 persons out of every 100,000 people
About 50% of congenital hearing loss is caused of genetic issues, and about 20% is due to cytomegalovirus (CMV) infection.
Consequences of newborn hearing loss
Hearing loss with newborns has the risk of causing delayed language acquisition, lowered academic achievement, social isolation,
and injury and can lead to increased social cost for addressing those issues.
The need to conduct hearing loss test for newborns
Unless hearing loss test is conducted, hearing loss is usually
discovered about 30 months after birth. And in this case, a child
fails to be stimulated with sounds, thus missing the most important
time period for linguistic development. If causes such as hereditary
or infectious) are accurately identified through hearing loss test immediately
after birth or within about 3 months and a child receives
appropriate treatment, lowered learning ability and developmental
disorder can be prevented.
Children with medium hearing loss can lead a normal life if they wear
hearing aids and receive appropriate treatment right after their birth.
Those with severe hearing loss can enjoy considerable help from cochlear
Genetic Eye (Ophthalmics) Disorder
Genetic test can exert various positive influences on the congenital
eye diseases which an individual and his or her congenital eye diseases.
DNA test involving accurate analysis and interpretation improves the
accuracy of consulting over genetic issues and can reduce the risk of
developing diseases or conduct treatment based on mechanism.
Humans have 46 chromosomes composed of 22 normal pairs of autosomes and
2 sex chromosomes. A chromosome has a large number of genes that contain
genetic information, so one more or less chromosome can exerts a huge
influence on the body. Frequently occurring abnormalities with the number
of chromosomes are Down syndrome, Edward syndrome, and Patau syndrome.
Turner syndrome occurs from missing X chromosome, and Klinefelter syndrome
is caused one more added X chromosome.
Types of chromosome abnormalities
Trisomy refers to the type with one additional specific chromosome.
Down syndrome, most known as chromosome abnormality, belongs to trisomy,
which has one more 21st chromosome added to it. Since a chromosome with
a larger size includes more genetic information, trisomy with large
chromosomes can have great influence on the body. So, many newborns with
Patau syndrome, which is made up of relatively large chromosomes, die
within several weeks from their birth.
Down syndrome, which is the most common chromosomal disorder,
is a genetic disorder in which three 21st chromosomes, which
is one more than the normal number, causes mental retardation,
physical deformity, kidney failure, and growth disorder. With
deformity appearing before birth and functional abnormalities
appearing after birth with several organs, it is a genetic
disorder that delivers a shorter life compared to ordinary people
and thus requires a broad range of medical and social supports
from birth to death.
Second to none in its frequency but Down syndrome,
Edward syndrome is a congenital deformity that occurs
from one more 18th chromosome to the normal number.
Such chromosomal abnormality causes deformity of body
organs such as heart, brain, or kidney and mental retardation,
in which case most newborns die within 10 weeks from their birth.
Patau syndrome is a congenital deformity that is
caused by one more 13th chromosome added to the
normal number. It is a congenital chromosomal anomaly
that shows severe deformity in the central nervous system.
Most newborns suffer natural miscarriage during pregnancy,
and those who make it to birth get to die during the newborn
period, with 90% of them dying within a year from their birth.
ㆍSex chromosome abnormalities
Sex chromosome abnormalities represent congenital chromosomal abnormalities,
either with missing or an extra sex chromosome. They seldom come with congenital
abnormalities with body organs, and show a minor reduction of intelligence.
But they more often than not brings problems during puberty.
Monosomy XTurner syndrome
Turner syndrome is a sex chromosome abnormality involving just one X chromosome
or structural abnormalities with one X chromosome (such as an abnormally small
size of the second X chromosome). These sex chromosome abnormalities, which cause
anomaly in heart or the musculoskeletal system, and in most cases require continuous
management including hormonal therapy.
In general, male sex chromosome has to have XY. And two or more X chromosomes constitute
Klinefelter syndrome. And it may cause various abnormalities as with intelligence, reproduction,
or body growth.
Pre-natal diagnosis of chromosomal abnormalities
Testing fetuses for sex chromosome abnormalities are divided into invasive test, which involves an analysis of collected amniotic fluid, and
non-invasive test, which taps into the mother's blood to scan the child's DNA included in it.
Comparison of pre-natal diagnostic tests for sex chromosome abnormalities
Real-time PCR based high-resolution genotyping technology
MeltingArray™ is a real-time PCR based diagnostic technology
that can identify mutation of specific sequences by using
specific hybridization of PNA.
Hereditary diseases can be diagnosed by identifying any presence of a DNA sequence that differs from
normal genes. Using MeltingArray can diagnose normal (left in the image), mutant (center in the image),
and both normal and mutant in possession (right in the image).
With MeltingArray, infectious diseases can be qualitatively and quantitatively analyzed, and it can also
conduct genotyping, antibiotic resistance analysis, multi-species analysis etc.