Tag: Genetic Disorders
-
Genetic Disorders: Definition, Development, and Examples
Continue ReadingWhat are Genetic Disorders
Genetic disorder is a condition where there is a mutation in a genetic material of an organism which leads to certain abnormalities.
We know that each cell in our body contains its one molecule of genetic material, which is known as DNA.
It encodes the cell to perform its particular function by giving instructions to the cell.
If there is any defect in the genetic material it leads to mutation or any other infections which leads to genetic disorders.
Cause of Genetic Disorders
Genetic disorders occurs when there is change in particular segment of a DNA or change or loss of a particular part of DNA or a whole chromosome, which is present within the body cells.
Almost all cells in our body contains an elongated strand of DNA. Each DNA is made of nucleosides and phosphate groups which encodes the cells to work in an appropriate manner so that the functioning of body remains stable.
DNA’s are placed in a chromosome, where each chromosome contains the small segment of DNA which is called as Genes.
It provides instructions to the body. Human body consists of about 23 pair of chromosomes where each parent sends their copy of one pair to their offspring’s, when such genes are passed to a next generation, a defect or mutation in a particular gene causes genetic disorder.
If the defect is passed from the past generations, it is said to be inherited. Only few people have this condition of getting inherited disorders.
Genetic disorders are classified into various types depending upon the defect in a chromosome or in a genome.
Before knowing about the disease-causing factors of gene it is important to about human genome.
Human Genome
All the gene and DNA which is required to build a human is referred to as human genome. Human Genome Project (HGP) is one of the global research projects which is used to map the human genome.
This project helps in sequencing the genes and to know about their different function.
HGP found that there are about 20,000 to 25,000 genes in the human genome. It also found the genomes and their appropriate functions which helped us to find the disease-causing factor of the genes depending upon the mutation in the bases of the DNA, such as adenine, thymine, guanine and cytosine.
Each DNA molecule is made up of two strands of DNA Which are coiled around each other in a form of a spiral ladder.
The bases are present in between the two strands, in a combination of adenine with thymine or cytosine with guanine.
A change in these combinations also leads to mutation. This change in order of these base pairs affect the instructions that are provided to the body to function.
DNA sequencing is referred too as reading of these base pairs. Thus, sequencing of genomes provides a better understanding in causative organism of diseases.
A change or fault in this condition of a DNA causes a genetic condition.
Since this genetic information is passed to their offspring’s through parents they are considered as inherited.
But not everyone from this generation will be affected by this because it also depends upon the passing of traits.
Genetic disorder has the capability to affect any of the genomes which involves many symptoms and causative factors.
Development of Genetic Disorders
Genetic characteristics pass from past generation through future generation between the families.
When parents pass their traits to the children, in some cases they tend to pass their disorders too. Each parent; both father and mother pass half a copy of their genes to their children which is commonly called as allele.
When two form of alleles are passed from parent to the children, the cells in the body of a offspring take the information from only one pair of that allele, which is known as dominant allele, and the other pair of alleles which is least concerned is referred to as recessive allele.
In such cases the person develops a genetic disorder if he gets either one of the dominant alleles or both the recessive allele from the infected parent.
Factors of Genetic Disorders
Genetic disorders are caused by many factors such as single gene inheritance, multifactorial inheritance, chromosomal inheritance and mitochondrial inheritance.
Single Gene Genetic Disorders
Single gene disorder is also known as monogenic disorder.
It is caused due to the mutations in a single gene caused in an individual and they are passed to the upcoming generations due to various factors such as Genomic imprinting and uniparental disomy.
Sometimes these conditions may also cause due to invitro fertilization.
In many cases, the congenital metabolic disorders, which are also known as inborn errors of metabolism are also due to single gene defects.
Single genes disorders also result in autosomal dominant disorders such as Huntington’s disease or Autosomal recessive disorders such as sickle cell disease, cystic fibrosis, phenylketonuria and thalassemia.Â
It also results in X-linked and Y- linked inherited disorders such as turners’ disorder.
Multifactorial Inheritance
Multifactorial inheritance is caused as a result of combination of both genetic factors and environment influences.
The non-genetic factors that influence the individual is smoking, alcohol, cancer, diabetes, multiple sclerosis and Alzheimer’s disease, etc.
Chromosomal Inheritance
Chromosomal abnormalities are due to the mutation or change in a chromosome of an individual such as having a lesser number of chromosomes than usual, having extra chromosomes or change in structure of any of the chromosomes.
Downs syndrome is one of the examples of chromosomal abnormality.
Mitochondrial Inheritance
This is also due to the single gene inherited disorder, it is also known as maternal inheritance and it occurs in rare cases than usual disorders.
This condition occurs as a result of defect in any of the 13 genes that are encoded by mitochondrial DNA, As the developing embryo gets its mitochondria from the egg cells.
In case the carrying mother is affected this disorder can pass to the offspring.
One of the examples of this type of disorder is Leber’s Hereditary optic neuropathy.
It is also important to know that many mitochondrial disorders are due to defect in the nuclear gene which resembles as such of autosomal recessive inheritance.
Genetic Disorders Diagnosis and Treatment
It is also to be clear that not every genetic disorder leads to death of a progeny. Even though there are no remedies for genetic disorders some can be diagnosed at an early stage.
The genetic disorders such as downs syndrome, and Muscular dystrophy shows no signs until turning into adult.
Even though there is no treatment there is chances of improving the quality of life than degradation such as physiological therapies and management of pain and choosing alternative medications.
Though the treatment of genetic disorders is not yet discovered or it is state of ongoing battle.
However, gene therapy plays an important role in bringing the normal healthy gene into a patient and removing the defective one.
Genetic Disorders Citations
- Genetic disorders. JEMS . 2014 Feb;39(2):64-71.
- Developmental Support for Infants With Genetic Disorders. Pediatrics . 2020 May;145(5):e20190629.
- Genetic Disorders of the Extracellular Matrix. Anat Rec (Hoboken) . 2020 Jun;303(6):1527-1542.
- Genetic disorders of nuclear receptors. J Clin Invest . 2017 Apr 3;127(4):1181-1192.
- Coatopathies: Genetic Disorders of Protein Coats. Annu Rev Cell Dev Biol . 2019 Oct 6;35:131-168.
- Maternal Genetic Disorders in Pregnancy. Obstet Gynecol Clin North Am . 2018 Jun;45(2):249-265.
Share
Similar Post:
-
Genetic Disorders: Definition, Cause, Symptoms, and Examples
Continue ReadingWhat are Genetic Disorders?
Genetic disorders are type of biological inheritance which follows the principles that have been proposed by Gregor Mendel in the year 1865 and 1866.
Generally, in humans the Genetic disorders are type of genetic cause which happens due to abnormalities or defects in the genome of an individual.
These disorders are seen in an affected individual from birth and can be diagnosed and can be treatment to reduce the impact even though it cannot be cured purely.
It can also be identified the passages of traits by pedigree analysis or family tree.
This type of genetic disorders is rare, affecting one of thousand individuals.
These disorders may or may not be inherited. Inherited disorders are the ones which are passed through germ line cells, where as in non-inheritable conditions these disorders are caused due to mutations or some changes in the genetic material.
A best example for this condition is cancer, which is either caused by environmental conditions or lifestyle factors or though inherited conditions.
Principles of Genetic Disorders
The research carried out by Mendel on pea plants stands as a base for understanding all the inheritances which are characterized by a single gene disorders.
Mendelian genetic disorders are caused due to a mutation in a single gene locus, where the locus is present in autosome or allosome.
It occurs either as a dominant or a recessive allele. If the individual who is having this disorder then the pedigree analysis is followed to find whether this disorder is present in an autosome or allosome in large families then dominant and recessive condition can also be found through that.
Mendel also suggested two laws for knowing the inherited disorders better.
Law of Segregation
Mendel’s law of segregation states that at the time of formation of genes two genes are separated so that each gene will carry one of the alleles.
Law of Independence
Mendel’s law of independence states that during the time of separation of gametes, each gene pair separates independently with other pairs.
It can also be said that the allele received by the gamete for one pair is independent of the allele received for the other allele.
Types of Genetic Disorders
Genetic disorders are classified depending upon the Mendel’s law of inheritance.
It is of five types namely;
 Autosomal dominant
 Autosomal recessive
 Sex-linked dominant
 Sex-linked recessive
 Mitochondrial
All these types of Mendelian disorders can be identified with the help of pedigree analysis.
Examples of Genetic Disorders
Examples of Mendelian Genetic disorders include;
 Sickle cell anaemia
 Muscular dystrophy
 Cystic fibrosis
 Thalassemia
 Phenylketonuria
 Colour blindness
 Skeletal dysplasia
 Haemophilia
Haemophilia
It is one of the types of sex-linked recessive disorder. Here, the unaffected carrier mother passes this condition to their sons.
This disorder is rare in females because they get only one gene through the parents at most of the times, so the probability will be as a carrier mother or as an unaffected one.
So, it is very rare that females will be an affected individual.
In this disorder the blood will not clot easily after an injury or any other accidents.
Males are most frequently affected to this type of disorder.
Sickle Cell Anaemia
It is one type of autosomal recessive disorder where the disorder is carried to the offspring’s if two parents are carriers of this disease.
This disorder is caused due to the mutation in the hemoglobin molecule where the glutamic acid present in the sixth position in a hemoglobin molecule in a beta chain is replaced by valine.
So, the hemoglobin molecules acquire a change in shape, by converting into a sickle shape from its normal biconcave shape which reduces the oxygen carrying capacity of the cells and this shape of molecules cannot be easily passed through the vascular system and it results in forming a block in small blood vessels such as capillaries.
Phenylketonuria
It is one of the autosomal recessive disorder caused due to the inborn error of phenylalanine metabolism which is one of the important amino acid needed for the body.
This disorder, affects the conversion of enzyme phenyl alanine into tyrosine as a result phenylalanine is being accumulated in the body which results in formation of many derivatives and causes mental retardation in most of the cases.
Thalassemia
It is one of the types of autosomal recessive disorder. In this type of disorder body makes abnormal amount of hemoglobin so it leads to a condition where higher amount of red blood cells is destroyed and causes anemia.
It causes symptoms such as abdominal swelling, dark urine excretion, deformities of facial bones etc.
Cystic Fibrosis
It is one of the types of autosomal recessive disorder where the lungs and digestive system gets affected completely and there is also a thick production or secretion of mucus which blocks the lungs and pancreas.
Usually, the person affected with this syndrome has very short life span.
Genetic Disorders Citations
- Genetic disorders. JEMS . 2014 Feb;39(2):64-71.
- Developmental Support for Infants With Genetic Disorders. Pediatrics . 2020 May;145(5):e20190629.
- Genetic disorders of nuclear receptors. J Clin Invest . 2017 Apr 3;127(4):1181-1192.
- Genetic Disorders of the Extracellular Matrix. Anat Rec (Hoboken) . 2020 Jun;303(6):1527-1542.
- Coatopathies: Genetic Disorders of Protein Coats. Annu Rev Cell Dev Biol . 2019 Oct 6;35:131-168.
- Maternal Genetic Disorders in Pregnancy. Obstet Gynecol Clin North Am . 2018 Jun;45(2):249-265.
Share
Similar Post:
