Galaktozeminin Genetiği
Galaktozemiden etkilenmeyen (ne taşıyıcı ne de galaktozemik) biri, GALT enzim (galaktozu vücut için kullanılabilir hale getirmek için gerekli enzim) üretimi için iki normal gen devralır. Bu kişinin genotipi N/N' dir ve enzim aktivitesi normal olur.
Klasik galaktozemi taşıyıcısı biri bir ebeveynden normal, diğerinden de klasik galaktozemiye yol açan hatayı kapsayan bir gen alır. Bu kişinin genotipi G/N' dir ve enzim aktivitesi normalden az ama tıbbi komplikasyonlara yol açacak ya da özel diyet yönetimi gerektirecek kadar da fazla değildir.
Klasik galaktozemisi olan biri her iki ebeveyninden de hatalı birer gen alır. Bu kişinin genotipi G/G' dir ve enzim aktivitesi aslında sıfırdır.
Duarte değişken genini içeren genotip aşağıdakileri içerir:
D/N = Duarte galaktozemi taşıyıcısı (yaklaşık %75 enzim aktivitesi)
D/D = homozigoz Duarte galaktozemi taşıyıcısı (yaklaşık %50 enzim aktivitesi)
D/G = Duarte galaktozemi (yaklaşık %25-50 enzim aktivitesi)
Yukarıdaki bilgiler ingilizceden çeviridir. Çeviriyi yapan www.pesekinovarus.org site yapımcısına göstermiş olduğu ilgi ve alakadan dolayı teşekkür ederim.
Çeviri metnini orjinal hali aşagıya çıkartılmıştır.
What is Classic Galactosemia?
Classic Galactosemia is a rare genetic metabolic disorder. The child with classic galactosemia inherits a gene for galactosemia from both parents, who are carriers. Patients who inherit the classic galactosemia gene from each parent are sometimes described as having the genetic makeup "G/G". Normally when a person consumes a product that contains lactose (e.g., dairy products such as milk, cheese, butter), the body breaks the lactose down into galactose and glucose. Glucose is the sugar used by the body for energy. Galactosemia means too much galactose in the blood caused by the individual "missing" the enzyme (known as GALT) to convert galactose into glucose. This accumulation of galactose is a poison to the body and can cause serious complications such as the following and if untreated, as high as 75% of infants will die:
an enlarged liver
kidney failure
cataract
brain damage
Diagnosis is made usually within the first week of life by blood test from a heel prick as part of a standard newborn screening. Treatment requires the strict exclusion of lactose/galactose from the diet. Although galactosemic children are started on diet restriction at birth, there continues to be a high incidence of long-term complications involving speech and language, fine and gross motor skill delays and specific learning disabilities. Ovarian failure may occur in girls. Prenatal diagnosis by amniocentresis is also available.
What is Duarte Galactosemia?
Duarte Galactosemia is a variant of classic galactosemia. Fortunately, the complications associated with classic galactosemia have not been associated with Duarte galactosemia. The child with Duarte galactosemia inherits a gene for classic galactosemia (G) from one parent, and a Duarte variant gene (D) from the other parent. Patients with this genetic make-up are frequently referred to as D/G galactosemics.
Diagnosis of Duarte galactosemia is made usually within the first weeks of life by the same blood test used to diagnose classic galactosemia. Galactose-1-phosphate uridyltransferase (GALT) enzyme activity in D/G patients is approximately 25%-50% of that found in children born with no galactosemia gene.
There is some disagreement over the need for dietary restriction in the treatment of children with Duarte galactosemia. Consult your medical advisors (preferrably a pediatric metabolic geneticist) for their advice on this topic. Dietary Options include :
restricting lactose / galactose in the diet for a year or so then gradually introducing these items and testing for the patient's response (i.e. elevation of galactose-1-phosphate (Gal-1-P) levels in patient's blood).
no restrictions at all, to include breastfeeding infants.
There is no research that conclusively reveals medical or other developmental complications attributable to Duarte galactosemia in D/G patients.
Genetics of Galactosemia
A person unaffected by galactosemia (neither carrier nor galactosemic) inherits two ‘normal' genes for the production of the GALT enzyme (the enzyme needed to convert galactose into a form useable by the body) . This person's genotype would be N/N and their enzyme activity would be normal.
A person who is a carrier of classic galactosemia inherits one normal gene from one parent and one gene containing the error that leads to classic galactosemia from the other parent. This person's genotype would be G/N and their enzyme activity would be less than normal, but not so much so as to cause medical complications or require dietary management.
A person who is classic galactosemic inherits two genes with the error, one from each of his/her parents. This person's genotype would be G/G and their enzyme activity would be essentially zero.
Genotypes involving the Duarte variant gene include:
D/N = carrier of Duarte galactosemia (about 75% enzyme activity)
D/D = homozygous carrier of Duarte galactosemia (about 50% enzyme activity)
D/G = Duarte galactosemia (about 25 - 50% enzyme activity ??)
Klasik galaktozemi taşıyıcısı biri bir ebeveynden normal, diğerinden de klasik galaktozemiye yol açan hatayı kapsayan bir gen alır. Bu kişinin genotipi G/N' dir ve enzim aktivitesi normalden az ama tıbbi komplikasyonlara yol açacak ya da özel diyet yönetimi gerektirecek kadar da fazla değildir.
Klasik galaktozemisi olan biri her iki ebeveyninden de hatalı birer gen alır. Bu kişinin genotipi G/G' dir ve enzim aktivitesi aslında sıfırdır.
Duarte değişken genini içeren genotip aşağıdakileri içerir:
D/N = Duarte galaktozemi taşıyıcısı (yaklaşık %75 enzim aktivitesi)
D/D = homozigoz Duarte galaktozemi taşıyıcısı (yaklaşık %50 enzim aktivitesi)
D/G = Duarte galaktozemi (yaklaşık %25-50 enzim aktivitesi)
Yukarıdaki bilgiler ingilizceden çeviridir. Çeviriyi yapan www.pesekinovarus.org site yapımcısına göstermiş olduğu ilgi ve alakadan dolayı teşekkür ederim.
Çeviri metnini orjinal hali aşagıya çıkartılmıştır.
What is Classic Galactosemia?
Classic Galactosemia is a rare genetic metabolic disorder. The child with classic galactosemia inherits a gene for galactosemia from both parents, who are carriers. Patients who inherit the classic galactosemia gene from each parent are sometimes described as having the genetic makeup "G/G". Normally when a person consumes a product that contains lactose (e.g., dairy products such as milk, cheese, butter), the body breaks the lactose down into galactose and glucose. Glucose is the sugar used by the body for energy. Galactosemia means too much galactose in the blood caused by the individual "missing" the enzyme (known as GALT) to convert galactose into glucose. This accumulation of galactose is a poison to the body and can cause serious complications such as the following and if untreated, as high as 75% of infants will die:
an enlarged liver
kidney failure
cataract
brain damage
Diagnosis is made usually within the first week of life by blood test from a heel prick as part of a standard newborn screening. Treatment requires the strict exclusion of lactose/galactose from the diet. Although galactosemic children are started on diet restriction at birth, there continues to be a high incidence of long-term complications involving speech and language, fine and gross motor skill delays and specific learning disabilities. Ovarian failure may occur in girls. Prenatal diagnosis by amniocentresis is also available.
What is Duarte Galactosemia?
Duarte Galactosemia is a variant of classic galactosemia. Fortunately, the complications associated with classic galactosemia have not been associated with Duarte galactosemia. The child with Duarte galactosemia inherits a gene for classic galactosemia (G) from one parent, and a Duarte variant gene (D) from the other parent. Patients with this genetic make-up are frequently referred to as D/G galactosemics.
Diagnosis of Duarte galactosemia is made usually within the first weeks of life by the same blood test used to diagnose classic galactosemia. Galactose-1-phosphate uridyltransferase (GALT) enzyme activity in D/G patients is approximately 25%-50% of that found in children born with no galactosemia gene.
There is some disagreement over the need for dietary restriction in the treatment of children with Duarte galactosemia. Consult your medical advisors (preferrably a pediatric metabolic geneticist) for their advice on this topic. Dietary Options include :
restricting lactose / galactose in the diet for a year or so then gradually introducing these items and testing for the patient's response (i.e. elevation of galactose-1-phosphate (Gal-1-P) levels in patient's blood).
no restrictions at all, to include breastfeeding infants.
There is no research that conclusively reveals medical or other developmental complications attributable to Duarte galactosemia in D/G patients.
Genetics of Galactosemia
A person unaffected by galactosemia (neither carrier nor galactosemic) inherits two ‘normal' genes for the production of the GALT enzyme (the enzyme needed to convert galactose into a form useable by the body) . This person's genotype would be N/N and their enzyme activity would be normal.
A person who is a carrier of classic galactosemia inherits one normal gene from one parent and one gene containing the error that leads to classic galactosemia from the other parent. This person's genotype would be G/N and their enzyme activity would be less than normal, but not so much so as to cause medical complications or require dietary management.
A person who is classic galactosemic inherits two genes with the error, one from each of his/her parents. This person's genotype would be G/G and their enzyme activity would be essentially zero.
Genotypes involving the Duarte variant gene include:
D/N = carrier of Duarte galactosemia (about 75% enzyme activity)
D/D = homozygous carrier of Duarte galactosemia (about 50% enzyme activity)
D/G = Duarte galactosemia (about 25 - 50% enzyme activity ??)
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