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Due to the heredity of the disease: a deep analysis of genetic factors in health and illness

I. The fundamental principles of heredity and genetic contribution

  1. Fundamentals of genetics: from DNA to phenotype:

    • DNA as an instruction of life: Deoxyribonucleic acid (DNA) is the basis of heredity. It contains genetic instructions that determine the development, functioning and characteristics of the body. DNA consists of nucleotides, each of which contains a nitrogen base (adenin, guanine, cytosine or thyamin), sugar (deoxybosis) and phosphate group. The sequence of these bases determines the genetic code.
    • Genes: units of heredity: Genes are DNA areas that encode certain proteins or perform regulatory functions. Squirrels are cage working horses, participating in all vital processes. The number of genes in the human genome is estimated at about 20,000 – 25,000.
    • Chromosomes: Organization of genetic material: DNA is organized in chromosomes, structures visible during cell division. A person has 23 pairs of chromosomes, 22 pairs by autosomes and one pair of sex chromosomes (XX in women, XY in men).
    • Genom: A complete set of genetic information: The genome is a complete set of DNA of the body, including all genes and non -leading sequences.
    • Genotype and phenotype: The genotype is the genetic composition of the body, and the phenotype is the observed characteristics, including physical, biochemical and behavioral characteristics. The phenotype is the result of the interaction of the genotype and the environment.

  2. Mechanisms of heredity: transmission of genetic information:

    • Meyos and Gamethogenesis: Meiosis is the process of dividing the cell, as a result of which gametes (spermatozoa and eggs) with a half set of chromosomes are formed. Hametogenesis is the process of formation of gametes.
    • Mendel’s laws: The laws of Mendel, opened by Gregor Mendel in the 19th century, describe the basic principles of inheritance of signs:
      • The law of the uniformity of the first generation hybrids: When crossing homozygous individuals that differ in one sign, all the first generation hybrids are uniform.
      • The law of splitting: When crossing the first generation hybrids in the second generation, there is a splitting of signs in a certain ratio (usually 3: 1 for dominant and recessive features).
      • Independent inheritance law: Genes located in different chromosomes are inherited independently of each other.
    • Inheritance, clutching with floor: Genes located on sex chromosomes (especially on the X-chromosome) are inherited in a special way, which leads to various manifestations in men and women.
    • Epigenetics: hereditary changes not related to the sequence of DNA: Epigenetics studies changes in genes expression that are not associated with changes in the sequence of DNA. These changes can be caused by environmental factors and can be inherited. Examples of epigenetic mechanisms include DNA methylation and histone modification.
    • Mitochondrial heredity: Mitochondria, organelles of cells with its own DNA (MTDNK) are transmitted along the maternal line. Mutations in MTDNK can cause various diseases.

  3. Types of inheritance: A variety of genetic models:

    • Autosomal dominant inheritance: To manifest the disease, one copy of the mutant gene is enough. Patients are usually found in each generation, and the probability of transmitting the disease to the offspring is 50%if one of the parents is sick.
    • Autosomal recessive inheritance: To manifest the disease, the presence of two copies of the mutant gene is necessary. Patients are usually born in healthy parents-carriers of a mutant gene. The probability of the birth of a sick child in two carrier parents is 25%.
    • X-linked dominant inheritance: The mutant gene is located on the X-chromosome. Sick women convey the disease 50% of their sons and daughters. Sick men convey the disease to all their daughters and none of the sons.
    • X-linked recessive inheritance: The mutant gene is located on the X-chromosome. Patients are more common in men, since they have only one X-chromosome. Women can be carriers of a mutant gene and not show the symptoms of the disease.
    • Y-linked inheritance: The mutant gene is located on the Y chromosome. The disease is transmitted only from father to son.
    • Multifactorial inheritance: The disease is the result of the interaction of many genes and environmental factors.

II. Classification of diseases due to heredity

  1. Chromosomal diseases: anomalies in the structure and number of chromosomes:

    • Aneuploidii: Changing the number of chromosomes. Examples:
      • Down Syndrome (Trisomy on the 21st Chromosome): It is characterized by mental retardation, characteristic features, heart defects and other anomalies.
      • Edwards Syndrome (Trisomy according to the 18th Chromosome): A severe disease characterized by multiple malformations, low survival.
      • Patau syndrome (trisomy according to the 13th chromosome): A severe disease characterized by multiple malformations, low survival.
      • Klainfelter syndrome (XXY): It is characterized by infertility, small testicles, high growth and other abnormalities in men.
      • Turner’s syndrome (x0): It is characterized by infertility, low growth, lack of secondary sexual characteristics and other abnormalities in women.
    • Structural abnormalities of chromosomes: Changes in the structure of chromosomes. Examples:
      • Deletions: Loss of part of the chromosome.
      • Duplications: Doubling part of the chromosome.
      • Inversions: The coup of the chromosome site is 180 degrees.
      • Translocations: Moving the chromosome section to another chromosome.
      • Ring chromosomes: Chromosome forming a ring.

  2. Monogenic diseases: diseases caused by mutations in one gene:

    • Autosomal dominant diseases:
      • Neurofibromatosis of type 1: It is characterized by the formation of tumors on the nerves, pigment spots on the skin and other abnormalities.
      • Huntington disease: Neurodegenerative disease, characterized by involuntary movements, mental disorders and dementia.
      • Achondroplasia: The form of dwarf, characterized by shortened limbs.
      • Marfan syndrome: The disease of connective tissue, characterized by high growth, long limbs, problems with the heart and eyes.
    • Autosomal recessive diseases:
      • Cykovyskidosis (cystic fibrosis): It is characterized by damage to the lungs, pancreas and other organs.
      • Phenylketonuria (FCU): Violation of phenylalanine metabolism, which can lead to mental retardation, if not treated.
      • Sickle-cell anemia: Blood disease characterized by an abnormal form of red blood cells.
      • Tey-Saxi disease: Neurodegenerative disease affecting the nerve cells of the brain and spinal cord.
    • X-scented diseases:
      • Hemophilia: Violation of blood coagulation, characterized by increased bleeding.
      • Dyushenna’s muscle dystrophy: A progressive muscle disease leading to disability.
      • Martin-Bella syndrome (brittle X-chromosome): The most common hereditary cause of mental retardation.

  3. Multifactorial diseases: diseases caused by the interaction of many genes and environmental factors:

    • Cardiovascular diseases: Ichemic heart disease, hypertension, myocardial infarction, stroke.
    • Diabetes: Type 1 and 2 diabetes.
    • Autoimmune diseases: Rheumatoid arthritis, systemic lupus erythematosus, multiple sclerosis.
    • Mental illness: Schizophrenia, bipolar disorder, depression.
    • Oncological diseases: Breast cancer, colon cancer, lung cancer.
    • Congenital malformations: Cuts of the lips and sky, congenital heart defects, defects in the nervous tube.

  4. Mitochondrial diseases: diseases caused by mutations in mitochondrial DNA:

    • MELAS (mitochondrial encephalomyopathy, lactacidosis and stroke -like episodes): It is characterized by mitochondrial encephalomyopathy, lactacidosis and stroke -like episodes.
    • Merrf (myoclonic epilepsy with “torn” muscle fibers): It is characterized by myoclonic epilepsy and “torn” muscle fibers.
    • Leia syndrome: Neurodegenerative disease affecting the central nervous system.

III. Diagnosis of hereditary diseases

  1. Prenatal diagnosis: Identification of diseases in the fetus:

    • Ultrasound examination (ultrasound): Used to visualize the fetus and identify anatomical anomalies.
    • Biochemical screening: Measurement of the levels of certain substances in the mother’s blood to assess the risk of chromosome anomalies.
    • Amniocentez: The foster fluid fence for the analysis of fetal cells.
    • Chorion Biopsy: The sample of the chorion tissue sample for analysis of fetal cells.
    • Cordocentesis: Blood sampling from the fetal umbilical cord for the analysis of fetal cells.
    • Non -invasive prenatal test (NIPT): Analysis of DNA of the fetus circulating in the blood of the mother.

  2. Postnatal diagnostics: identification of diseases after birth:

    • Clinical examination: Assessment of the physical condition and symptoms of the patient.
    • Genealogical analysis: The study of the patient’s family history to identify hereditary diseases.
    • Cytogenetic analysis (karyotyping): Analysis of chromosomes to detect chromosomal abnormalities.
    • Molecular genetic analysis: DNA analysis for identifying mutations in genes.
      • DNA sequencing (including sequencing of the entire genome and exom): Determination of the sequence of DNA.
      • PCR (polymerase chain reaction): An increase in the number of a specific DNA section for analysis.
      • Fish (fluorescent hybridization in situ): The method used to detect certain DNA sequences on chromosomes.
    • Biochemical tests: Measurement of the levels of certain substances in the blood, urine or other biological fluids to detect metabolic disorders.

  3. Preimplantation genetic diagnostics (PGD): Identification of diseases in embryos before implantation:

    • PGD ​​is carried out in the framework of IVF (extracurporeal fertilization). The embryos obtained as a result of IVF are subjected to genetic analysis, and only healthy embryos are implanted into the uterus.

  4. Newborns screening: identification of diseases at an early stage to prevent serious consequences:

    • Screening of newborns allows you to identify diseases that can lead to serious consequences if they are not treated at an early stage. Examples of diseases detected during newborns screening include phenylketonuria, hypothyroidism, galactocurium and cystic fibrosis.

IV. Treatment of hereditary diseases

  1. Drug therapy: the use of drugs to relieve symptoms and slow down the progression of the disease:

    • Pharmacological correction of metabolic disorders: For example, the use of enzyme preparations for phenylketonuria or galactosemia.
    • Symptoms treatment: The use of drugs to relieve pain, seizures, muscle weakness and other symptoms.
    • Target therapy: The use of drugs aimed at certain molecules or mechanisms involved in the development of the disease.

  2. Surgical treatment: correction of anatomical defects and elimination of tumors:

    • Correction of congenital heart defects: Surgical correction of heart defects.
    • Removing tumors with neurofibromatosis: Surgical removal of tumors on the nerves.
    • Organ transplantation: Organs transplant (for example, liver for cystic fibrosis).

  3. Gene therapy: the introduction of a functional gene into the patient’s cells to replace the mutant gene:

    • Gene therapy is a promising method of treating hereditary diseases. It consists in introducing a functional gene into the patient’s cells to replace the mutant gene.
    • Various approaches to genetic therapy:
      • Vector gene therapy: The use of viruses as vectors for the delivery of gene to cells.
      • Unprofitable gene therapy: The use of other methods for delivering gene to cells, such as liposomes or electrophy.
    • Examples of successful genetic therapy:
      • Spinal muscle atrophy (SMA): Genetical and therapy preparations have been developed that significantly improve the survival and quality of life of patients with SMA.
      • Some forms of hereditary blindness: Gene therapy has shown the effectiveness in the treatment of some forms of hereditary blindness caused by mutations in the RPE65 gene.

  4. Cell therapy: the use of cells to restore damaged tissues and organs:

    • Cell therapy consists in the use of cells to restore damaged tissues and organs.
    • Examples of cell therapy:
      • Bone marrow transplantation: Used to treat certain diseases of the blood and immune system.
      • Stem cell transplantation: It is investigated for the treatment of various diseases, including neurodegenerative diseases and trauma of the spinal cord.

  5. Rehabilitation and supportive therapy: Improving the quality of life of patients:

    • Physiotherapy: Improving motor functions and preventing contractures.
    • Labor therapy: Improving self -service skills.
    • Speech therapy: Improving speech and communication.
    • Psychological support: Assistance to patients and their families in adaptation to the disease.
    • Diet therapy: Compliance with a certain diet for controlling metabolic disorders.

V. Prevention of hereditary diseases

  1. Genetic counseling: assessment of the risk of inheritance of the disease and providing information:

    • Genetic counseling is carried out by a geneticist and includes an assessment of family history, conducting genetic tests and providing information about the risk of inheritance of the disease, available methods of diagnosis and treatment.

  2. Prenatal diagnosis and preimplantation genetic diagnostics: identification of diseases in the early stages and preventing their transmission:

    • Prenatal diagnosis allows you to identify diseases in the fetus in the early stages of pregnancy and decide on the abortion in case of a serious illness.
    • PGD ​​allows you to identify diseases in embryos before implantation and implant only healthy embryos.

  3. Newborns screening: identification of diseases at an early stage to prevent serious consequences:

    • Screening of newborns allows you to identify diseases that can lead to serious consequences if they are not treated at an early stage.

  4. Preventive measures: reducing the risk of developing multifactorial diseases:

    • Healthy lifestyle: Proper nutrition, regular physical exercises, rejection of smoking and alcohol abuse.
    • Vaccination: Prevention of infectious diseases that can contribute to the development of certain multifactorial diseases.
    • Avoiding the effects of harmful environmental factors: Reducing the effects of toxic substances, radiation and other harmful environmental factors.

VI. Ethical and social aspects of genetic testing and treatment of hereditary diseases

  1. Confidentiality of genetic information: Protection of genetic information from unauthorized access and use.
  2. Nediscrimination based on genetic information: A ban on discrimination of patients on the basis of their genetic information in the field of employment, insurance and other areas of life.
  3. Informed consent to genetic testing and treatment: Providing patients with complete and understandable information about genetic testing and treatment so that they can make a conscious decision.
  4. The availability of genetic tests and treatment: Ensuring equal access to genetic tests and treatment for all patients, regardless of their social status and place of residence.
  5. Reproductive solutions: Providing patients with information about reproductive capabilities, such as prenatal diagnosis, PGD and the use of donor sperm or eggs.
  6. Gene editing: Ethical issues related to the use of gene editing technologies, such as CRISPR-CAS9, for the treatment of hereditary diseases.

VII. Modern research in the field of hereditary diseases

  1. Development of new genetic testing methods: Development of faster, accurate and affordable methods of genetic testing.
  2. Search for new genes responsible for hereditary diseases: The identification of new genes, mutations in which are caused by hereditary diseases.
  3. Development of new methods of treating hereditary diseases: Development of new treatment methods such as gene therapy, cell therapy and targeted therapy.
  4. Studying the role of epigenetics in the development of hereditary diseases: The study of the role of epigenetic mechanisms in the development of hereditary diseases and the development of methods of epigenetic therapy.
  5. Development of new methods for the prevention of hereditary diseases: Development of new methods of prevention, such as early diagnosis and preventive treatment.

VIII. Conclusion

Hereditary diseases are a serious healthcare problem. Understanding the genetic mechanisms underlying these diseases is crucial for the development of effective methods of diagnosis, treatment and prevention. Modern studies in the field of genetics and genomics open up new opportunities for improving the health and quality of life of people suffering from hereditary diseases. Genetic counseling, prenatal diagnosis, screening of newborns, gene therapy, cell therapy and preventive measures play an important role in reducing the burden of hereditary diseases. It is important to take into account the ethical and social aspects of genetic testing and treatment in order to provide fair and equal access to these technologies for all patients.

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