What Are Different Types of Genetic Disorders?

Disease name

[yí chuán bìng]

Genetic diseases are diseases caused by changes in genetic material or controlled by disease-causing genes. A genetic disease is a disease that is completely or partially determined by genetic factors. It is usually congenital and can also develop onset. Such as congenital stupidity, multi-finger (toe), congenital deafness, hemophilia, etc. These genetic diseases are completely determined by genetic factors, and they occur only after a certain period of time, sometimes after several years, ten years or even It will take ten years for the symptoms to show up.

Basic introduction to genetic diseases

Disease name

yichuanbing

Genetic disease

genetic diseases

Brief introduction to the disease: if the muscular dystrophy of the muscular dystrophic muscle does not develop until childhood; chronic progressive chorea is generally manifested in the middle age. Some genetic diseases require the combined action of genetic factors and environmental factors, such as asthma. Genetic factors account for 80% and environmental factors account for 20%. Gastric and duodenal ulcers, genetic factors account for 30% to 40%, and environmental factors account for 60% to 70%. Genetic diseases often occur in multiple people in a family, and they are familial, but it is also possible that there is only one patient in a family, which is sporadic, such as phenylketonuria. Recessive chromosomal genetic disease. Only when both spouses carry a gene that causes the disease, the child will become homozygous for the recessive disease-causing gene (both genes in the same gene locus are abnormal) and become sick. Therefore, it is mostly distributed, especially in families with only one child. It is not surprising that patients with genetic diseases occasionally circulate.

Main types of genetic diseases

Disease types : Diseases caused by changes in genetic material, including chromosomal aberrations and genetic mutations that are not visible at the chromosome level, are collectively referred to as genetic diseases. According to the procedures for changing the genetic material involved, genetic diseases can be divided into three categories:

Genetic disease related pictures (8 photos)

One is chromosome disease or chromosome syndrome . Changes in genetic material are visible at the chromosome level, manifested as changes in number or structure. Due to the large number of genes involved in chromosome disease, symptoms are usually severe, involving multiple organ and system distortions and functional changes.

The second is a single gene disease . At present, more than 6,500 types of single gene diseases have been found, mainly referring to diseases caused by mutations in a pair of alleles, which are caused by dominant gene and recessive gene mutations, respectively. The so-called dominant gene refers to a gene that causes disease if only one of the alleles (a pair of homologous chromosomes controls relative traits at the same position) is mutated. A recessive gene is a gene that can cause disease only when a pair of alleles are mutated at the same time.

The third is polygenic disease . As the name implies, this type of disease involves multiple genes. Unlike single gene disease, these genes have no dominant and recessive relationship. Each gene has only a minor cumulative effect, so the same People with different diseases may have significantly different disease severity and recurrence risk due to the difference in the number of causative genes that may be involved, and they show a family aggregation phenomenon, such as cleft lip, which is mild and severe, and some people are also accompanied by There are cleft palate. It is worth noting that in addition to genetics, polygenetic diseases are also affected by environmental factors, so they are also called multifactorial diseases. Many common diseases such as asthma, cleft lip, schizophrenia, anencephaly, hypertension, congenital cardiovascular disease, epilepsy, etc. are polygenic diseases.

So, can genetic diseases be treated? Previously, genetic diseases were considered incurable. In recent years, with the development of modern medicine, medical genetics researchers have clarified the pathogenesis of some genetic diseases in the study of genetic diseases, thus providing a certain basis for the treatment and prevention of genetic diseases, and continue to propose New treatments.

Hereditary pathology

1. Chromosomal abnormalities refer to diseases caused by abnormal numbers or morphology and structure of chromosomes:

A. Structural abnormal meow syndrome (partial deletion of chromosome 5)

B. Abnormal number of autosomes: Trisomy 21

Sex chromosomes: hypogonadism (X0, XXY, XYY)

2. Genetic abnormalities

A, single gene

Genetic disorders caused by abnormalities in genes on a pair of chromosomes from a father or mother in a homologous chromosome.

a. Autosomal Dominance

(Cartilage hypoplasia, polydactyly, colon polyps),

Recessive

(Albinism, phenylketonuria, melena, congenital deafness, high myopia),

Incompletely dominant (thalassemia)

b. Sex chromosomes . Incidence of X-dominant women is higher than men

(Xg blood type, also like vitamin D rickets),

Recessive men have a higher incidence than women

(Red-green blindness, hemophilia, etc. are more common)

with Y only onset in men (external auditory hirsutism)

B. Multiple genes

Genetic disorders associated with more than two pairs of genes. There is no dominant or recessive relationship between each pair of genes, and each disease is affected by multiple pairs of genes and environmental factors

Essential hypertension, bronchial asthma, coronary heart disease, juvenile diabetes,

Rheumatoid arthritis, schizophrenia, epilepsy, congenital heart disease,

Peptic ulcer, varicose veins of lower limbs, glaucoma, kidney stones, spina bifida,

No brain child, cleft lip, cleft palate, deformed foot, etc.

Common genetic diseases and their prevention

Genetic diseases are diseases caused by changes in genetic material. Congenital, lifelong and familial. There are many diseases and high incidence. At present, more than 3,000 genetic diseases have been discovered, and it is estimated that about 3 to 10 of every 100 newborns have various degrees of genetic diseases.

Genetic disease hypertension

Genetic risk:

Scientists have successfully developed a "hereditary spontaneous hypertension" mouse. These mice pass on the gene of high blood pressure from generation to generation, and their offspring will develop hypertension 100%, which is the most typical example of high blood pressure and genetics.

At present, most scholars believe that hypertension is a polygenic inherited disease. According to a family survey of hypertension patients, it is found that parents have hypertension, and their children will have a high probability of high blood pressure in the future; 45% of parents have high blood pressure, and their children have a 28% chance of developing high blood pressure; The probability of a child having hypertension is only 3%.

Prevention principle

1. Persist in monitoring blood pressure, at least once a year under normal conditions.

2. Limit salt and potassium. Gradually control the daily intake of salt to 5 grams, and eat more potassium-rich fruits and vegetables (such as bananas, walnuts, lotus seeds, amaranth, amaranth, spinach, etc.).

3. Prevent overweight and obesity.

4. Quit smoking and limit alcohol.

Genetic disease diabetes

Genetic risk:

Diabetes has a significant genetic susceptibility (especially the most common type 2 diabetes in clinical settings). Pedigree research found that the prevalence of diabetes in people with a positive family history of diabetes was significantly higher than in people with a negative family history. For parents who have diabetes, their children are 15-20 times more likely to develop diabetes.

Prevention principle

The "external causes" of diabetes include too much caloric intake, decreased activity, obesity, smoking, and excessive psychological stress. In turn, avoiding these factors can prevent diabetes. In terms of diet, a reasonable mix of food, meat, eggs, milk, vegetables, and fruits should be achieved, and the intake and consumption should be balanced. Always measure your weight. If you gain weight, you must be over calories. You should review your recipes and increase exercise.

Dyslipidemia

Genetic risk:

There are many causes of abnormal lipid metabolism, one of which is genetic factors. With the development of medical science, it has been found that quite a few patients with dyslipidemia have one or more genetic defects. Dyslipidemia caused by genetic defects are mostly family-aggregated and have a significant genetic tendency. They are clinically referred to as familial dyslipidemia.

Prevention principle

The most important thing is to emphasize "open your legs and keep your mouth shut." On the one hand, the diet should be appropriately restricted, but the variety of food should be as rich as possible. Use low-fat foods (vegetable oil, yogurt), increase vitamins and fiber (fruits, vegetables, bread and cereals) to control weight. At the same time, strengthen exercise so that calories are consumed so that fat does not accumulate in the body.

Genetic disease breast cancer

Genetic risk:

Breast cancer has a clear familial genetic predisposition. Epidemiological investigations found that 5% to 10% of breast cancers are familial. If one close relative has breast cancer, the risk of developing the disease increases 1.5 to 3 times; if two close relatives have breast cancer, the prevalence will increase 7 times. The younger the age of onset, the greater the risk of breast cancer among relatives.

Prevention principle

Those with a family history of breast cancer should pay special attention to self-examination to find clues to breast cancer and early treatment. Breast mass is the most common sign of breast cancer. This kind of mass is different from breast hyperplasia mass. It is often single, irregular in shape, hard in texture, poor in activity, mostly painless, and has no obvious relationship with the menstrual cycle. In addition, if you find nipple eczema, discharge, or shrinkage, you should also pay attention to it and go to the hospital for further examination.

Genetic disease gastric cancer

Genetic risk:

Patients with gastric cancer have obvious familial aggregation. The survey found that the first-degree relatives (ie parents and siblings) of patients with gastric cancer have an average three times higher risk of gastric cancer than the general population. The more famous family is Napoleon. His grandfather, father, and three younger sisters died of gastric cancer. A total of 7 people, including himself, suffered from gastric cancer.

Prevention principle

Risk factors for gastric cancer include lack of physical exercise, mental depression, smoking, smoking smoked foods, heavy salt diets, excessive meat intake, Helicobacter pylori infection, and gastric ulcers. And edible fungi, fresh fruits are protective factors of gastric cancer. It is worth noting that the family aggregation phenomenon of gastric cancer may be related to co-infection with Helicobacter pylori. Those with a family history of gastric cancer should go to the hospital to monitor for the bacterial infection and treat it in time.

Genetic disease colorectal cancer

Genetic risk:

Colorectal cancer caused by family inheritance accounts for 10% to 15% of the total number of people with colorectal cancer. People with colorectal cancer among their relatives are 3 to 4 times more likely to develop this disease than ordinary people. If two or more close relatives (parents or siblings) in the family have colorectal cancer, they are at high risk for colorectal cancer. .

Prevention principle

People with a family history of colorectal cancer should eat more fresh foods, less pickled and smoked foods, not moldy foods, drink less alcoholic beverages, and quit smoking. If the following symptoms occur, go to the hospital for examination:

Changes in bowel habits, increased bowel frequency, or alternate appearance of diarrhea and constipation. stool with pus or bloody mucus. The stool becomes thin and deformed, and the defecation is laborious. I have a bowel movement from time to time, but no bowel movements.

Genetic disease lung cancer

Genetic risk:

Foreign research institutions have conducted a follow-up survey of more than 102,000 Japanese middle-aged and elderly people for 13 years, and a total of 791 cases of lung cancer appeared in the Chinese Communist Party. The researchers compared the two groups of direct relatives with and without lung cancer, and found that the former was twice as likely to develop the disease. The inheritance of lung cancer is particularly evident in women.

Prevention principle

The occurrence of lung cancer is closely related to smoking, especially those with a family history of lung cancer, they must stay away from tobacco and passive smoking. If there are symptoms such as irritating cough, sputum and blood, especially the above-mentioned high-risk groups, you should consult a doctor as soon as possible. If early detection and standardized treatment can be achieved, the cure rate of lung cancer can reach 70%.

Genetic disease asthma

Genetic risk:

At present, most scholars believe that the genetic factors of asthma are greater than the environmental factors. If both parents have asthma, their child may have asthma as high as 60%; if one parent has asthma, the child is 20% more likely to have asthma; if neither parent has asthma, the child is only 6 %about. In addition, if family members and their relatives suffer from allergic diseases such as allergic rhinitis, skin allergies, or food and drug allergies, the risk of asthma in offspring will also increase.

Prevention principle

Adult asthma usually develops in childhood. Early childhood treatment is the key to reducing the incidence of adulthood. Those with a family history of asthma should avoid various environmental factors that cause asthma, such as inhalation of allergic substances (allergens), respiratory virus and bacterial infections, smoking and air pollution, etc. These factors trigger and contribute to the onset and exacerbation of asthma. Role. In general, we must do a good job in the cleanliness of the living room, living and working environment, quit smoking, and actively prevent and timely treat respiratory infections.

Genetic disease depression

Genetic risk:

Many studies have found that the occurrence of depression is closely related to genetic factors. The relatives of depression patients have a much higher probability of depression than ordinary people, about 10 to 30 times, and the closer the blood relationship, the more likely the disease is. high. According to foreign reports, the probability of depression among relatives of depression patients is: 14% of first-degree relatives (parents, siblings, children) and second-degree relatives (uncle, uncle, aunt, aunt, grandmother, grandparent or grandchild, grandmother) (Nephew) was 4.8%, and third-degree relatives (cousin, cousin and sister) were 3.6%.

Prevention principle

The prevention and treatment of depression should be based on early detection, early diagnosis and early treatment. If you often feel unhappy, significantly increase or decrease in weight, insomnia or excessive sleep, restlessness, inattention, light thoughts, etc., go to the hospital for treatment in time.

Alzheimer's disease

(Commonly known as dementia)

Genetic risk:

After long-term research, scientists have discovered that Alzheimer's disease is a polygenic genetic disease. Studies have found that patients with Alzheimer's disease in parents or brothers are four times more likely to develop Alzheimer's disease than those without family history.

Prevention principle

If you have a family history of Alzheimer's disease, you should check it after you are 50 years old to see if you have an intellectual disability so that you can take some measures in time for treatment.

In addition to genetic factors, people with low levels of education are susceptible to Alzheimer's disease, while those with formal education have a 7 to 10-year delay in onset of age than those without education. In addition, long-term emotional depression, solitary living, low cultural and language levels, widowed and no longer married, not participating in social activities, lack of physical and mental activities are also prone to Alzheimer's disease.

Genetic disease overweight

The genetic factors of weight of obese people account for 25% -40%. Should control the intake of fats and sweets, exercise regularly.

Genetic disease osteoporosis

The bone condition of a woman is very similar to that of her mother. Prevention should increase calcium and vitamin D intake.

Genetic disorders erectile dysfunction

Its two major causes are closely related to heredity: one is psychological factors, and the other is factors such as heart disease, diabetes and hypertension.

Summary of Genetic Diseases

Among them, the incidence of type 1 to 10 genetic diseases is about 30%, and there is a trend of increasing year by year. Therefore, he can no longer generalize that genetic disease is only a rare disease. Preventing the birth of children with genetic diseases is an important eugenic method to improve the quality of the Chinese population. Most genetic diseases cannot be cured. Because modern medicine cannot alter the genes of a person who has been born, as long as the disease-causing gene is still present, there is no cure. But some diseases can be alleviated by continuous medication.

Hereditary diseases

Hereditary diseases are diseases caused by changes in genetic material.

Genetic diseases are congenital, familial, lifelong, and hereditary.

The types of genetic diseases can be roughly divided into four categories:

Single gene disease

Autosomal dominant hereditary disease: hereditary characteristics are continuous heredity, no gender difference, familial aggregation, etc.

Autosomal recessive genetic disease: genetic characteristics include intergenerational performance, no gender differences, such as albinism, phenylketonuria, congenital deafness, sickle cell anemia, infantile idiot

X chromosome dominant hereditary disease: hereditary characteristics are continuous heredity, cross heredity, more women than men, the daughters of male patients are patients, such as anti-vitamin D rickets, hereditary nephritis, etc.

Recessive genetic disease of X chromosome: hereditary characteristics are intergenerational heredity, cross heredity, and more men than women, such as hemophilia, progressive muscular dystrophy (hypertrophy), and color blindness.

Y chromosome genetic disease: it is characterized by hereditary and continuous heredity, such as hirsutism in the external ear canal.

polygenic disease

It is controlled by multiple pairs of genes, showing a trend of family aggregation, which is difficult to predict. There are no good prevention programs, such as cleft lip, anencephaly, primary hypertension, and juvenile diabetes.

chromosome disease

Diseases with abnormal number of chromosomes: such as "trisomy 21" syndrome, also known as congenital stupidity and Down's syndrome, is formed by an additional number of chromosome 21; hypogonadism, also known as Turner's syndrome Symptoms are caused by the absence of one female X chromosome. The reason for this is that meiotic abnormalities form male and female gametes that do not contain sex chromosomes and a fertilized egg formed by the combination of a normal heterotypic gamete with X chromosomes. : Male XXY, the fertilized eggs forming this individual may be formed by a female gamete containing the XX chromosome and a male gamete containing the Y chromosome, or it may be a normal female gamete and another male gamete containing the XY chromosome Combined.

Diseases with abnormal chromosomal structure: such as meow syndrome is caused by the partial deletion of chromosome 5.

Cytoplasmic genetic disease

Cytoplasmic genetic material exists only in mitochondria, so cytoplasmic genetic disease is mitochondrial genetic disease, and common cases include neuromuscular weakness. Because the cytoplasm in fertilized eggs is mainly derived from egg cells, cytoplasmic genetic diseases depend on the mother and are characterized by "maternal disease and children's disease".

Basic Therapy for Genetic Diseases

Genetic disease diet therapy

Certain genetic diseases can be controlled by diet to prevent the disease from occurring, and thus receive therapeutic effects. For example, the pathogenesis of phenylketonuria is a deficiency of phenylalanine hydroxylase, which causes phenylalanine and phenylpyruvate to accumulate in the body and cause disease. Children with mental retardation or idiots may appear. However, if the diagnosis is accurate, it is best to start the prevention and treatment in 7-10 days after birth. Within 3 months after birth, give the child a low-phenylalanine diet, such as rice, cabbage, spinach, potato, mutton, etc. , Can promote normal growth and development of babies. When your child grows up to school, relax the restrictions on diet.

For another example, 5% of people in the provinces south of the Yangtze River in China suffer from hereditary glucose 6-phosphate dehydrogenase deficiency, and Linqing presents with hemolytic anemia, which can be life-threatening in severe cases. This type of patient is particularly sensitive to broad beans, which can cause acute hemolytic anemia after eating broad beans, so it is also called "faba bean disease". For these patients, faba beans and their products should be strictly fasted. At the same time, this disease can also cause drug-induced hemolysis, infectious hemolysis, and hereditary non-spherical cell hemolytic anemia, etc. Therefore, medication must be used with caution.

Genetic disease medication

Drugs often play a certain auxiliary role in the treatment of genetic diseases, thereby improving the patient's condition and reducing pain. It is mainly symptomatic treatment, such as taking analgesics to reduce patient pain. It can also improve the body's metabolism, such as degeneration of the liver-like bean nucleus, which is mainly a disorder of copper metabolism in the body, which increases the level of copper in the blood and causes fetal malformations. You can take drugs that promote copper excretion, and at the same time limit the consumption of copper-containing foods to maintain the normal level of copper in the body and achieve good therapeutic effects. Some diseases, such as congenital hypoimmunoglobulinemia, can be injected with immunoglobulin preparations to achieve the purpose of treatment.

Genetic disease surgery

Surgical correction refers to the method of surgically removing certain organs or repairing some organs with morphological defects. For example, spherocytosis, due to genetic defects, the patient's erythrocyte membrane osmotic fragility is significantly increased, and the red blood cells are spherical. Such red blood cells are easily destroyed when passing through the spleen and sinus, causing hemolytic anemia. Splenectomy can be performed. Although the abnormal shape of red blood cells cannot be changed after splenectomy, it can prolong the life of red blood cells and obtain a therapeutic effect. For multi-finger, rabbit lip and external genital deformities, etc., it can be corrected by surgery. Another example is that body odor is also a genetic disease, but as long as the glands secreted by the patient's underarms are removed, the patient can be eliminated.

Genetic Therapy for Genetic Diseases

Gene therapy inheritance is a fundamental and promising approach. Human genetic material can also be borrowed from other creatures like the story of "shrimp borrowing eyes from earthworms". That is, normal genes are injected into cells with defective genes to achieve therapeutic purposes. Gene therapy is simple to say, but it is actually quite a complex problem. Defective genes must first be found from hundreds of thousands of genes. At the same time, corresponding normal genes must be prepared, and then the normal genes can be transferred into cells to replace the defective genes and be able to perform normal expression. This treatment is still in the research and exploration stage.

It is worth mentioning that at the current stage of gene therapy that has not been thoroughly studied, genetic diseases can be treated with the above simple methods, after all, only a few, and this type of treatment only has the effect of treating the symptoms, the so-called "phenotype "Treatment" can only eliminate the pain of a generation, but has not touched the pathogenic gene itself. Those disease-causing genes will, as always, be passed on to future generations of patients in accordance with inherent laws.

Genetic disease analysis and research

Diseases caused by changes in genetic material before or during the formation of a fertilized egg. Some people think that only the diseases determined by the genetic factors of parents are genetic diseases, and this understanding is not comprehensive. For example, some chromosomal aberrations are not determined by genetic factors of the parents, but are generated during the formation of fertilized eggs. Traditionally, chromosome aberrations are included in the category of genetic diseases. Some people think that all diseases affected by genetic factors are genetic diseases, and the concept is not precise, because in all human diseases, except for a few (such as trauma caused by fractures), they are completely caused by environmental factors and are not affected by genetic factors. In addition to the effects, almost all diseases are the result of the interaction between environmental and genetic factors, but the degree to which the two affect the disease can be different. Even if the disease has obvious environmental factors such as bacterial infection and epilepsy after trauma, there are differences in susceptibility among different individuals, and this difference is also affected by genetic factors. It is impossible to include these diseases in the category of genetic diseases. In. Diseases that are completely determined by genetic factors (type A, such as trisomy 21) and those that are completely determined by environmental factors (type D, such as traumatic fractures) are a minority, while most human diseases are in categories B and C class. Type B refers to basically genetic factors, but it needs certain incentives in the environment to develop the disease. For example, children with phenylpyruvate will develop phenylalanine after birth. Type C refers to diseases in which both genetic and environmental factors contribute to the onset of disease, such as hypertension and infection; however, the heritability of different diseases is different, that is, the greater the influence of genetic factors, the higher the heritability. Therefore, in theory, the three types of A, B, and C are genetic diseases, but the type C such as infection and post-traumatic epilepsy are not customarily included in the category of genetic diseases. Genetic disease is different from congenital disease, which refers to a disease that has been manifested at birth. Although many genetic diseases are manifested at birth, there are also some genetic diseases that appear normal at birth, but only gradually appear after a few days, months, or even years, decades. This is obviously Not a congenital disease. On the other hand, congenital diseases are not caused by genetic factors. For example, congenital malformations caused by pregnant mothers when they are exposed to radiation are not genetic diseases. Genetic diseases are also different from familial diseases. Although some family members can express genetic diseases because the same family members have the same genetic basis, the transmission laws of different genetic diseases between parents and offspring are complex and diverse, and some genetic diseases (such as recessive inheritance such as albinism) Disease) may not have a family history. On the other hand, familial diseases may also be caused by non-genetic factors (such as the same living conditions), such as lack of vitamin A in the diet, causing night blindness in multiple family members.

In the past, genetic disease was considered to be a relatively rare disease. However, with the development of medicine and the improvement of people's living standards, some infectious and nutritional diseases that have seriously threatened human health in the past have been controlled, and genetic diseases have become a more prominent problem. For example, a survey of the cause of death of children in Britain in 1914 showed that non-hereditary diseases (such as infections and tumors) accounted for 83.5%, while hereditary diseases accounted for only 16.5%, but by the late 1970s, two types of diseases accounted for 50% each. %. The situation is the same in China. Among infectious diseases of children in Beijing in 1951, infectious diseases play an important role. However, in the analysis of childhood deaths from 1974 to 1976, congenital malformations accounted for 23.4% of all deaths, ranking first. Among the malformations, 3 to 10 are genetic diseases. On the other hand, there are many types of genetic diseases. With the development of biology and medicine, new genetic diseases have been discovered in recent years. It shows that about 4,000 kinds of genetic diseases of humans have been recognized by people from 1958 to 1982.

A Brief History The 18th-century Frenchman Mopeletti first conducted a pedigree survey of genetic diseases, and he analyzed the hereditary patterns of albinism. In 1814 Adams published a paper on the genetic properties of clinical diseases, which is considered to be the earliest modern article to systematically discuss genetic diseases. In 1908, AE Garrodt first proposed the concept of "congenital metabolic abnormalities", linking heredity and metabolism, and believed that the genetic laws of inborn metabolic abnormalities such as uric aciduria could be explained by Mendel's law, which made an epoch-making revolution for medical genetics. Contribution. In 1949, L. Pauling proposed the concept of "molecular disease". In 1944, Bicker first proposed that controlling neonatal nutrition can effectively prevent the development of phenylpyruvateuria, and opened a new chapter for the effective treatment of genetic diseases. In 1958, J. Legener discovered that children with congenital stupidity were three chromosomes 21, which was the first report of a chromosomal abnormality in a genetic disease. In 1969, Labus discovered the fragile part of the X chromosome, which opened a new field for the study of chromosome aberrations. Since the 1960s, prenatal diagnosis of genetic diseases has been applied to the clinic. In 1978, Kahn and Dozi applied DNA recombination technology to the diagnosis of genetic diseases for the first time. They diagnosed a case of sickle cell anemia, and this diagnostic technology has developed rapidly since then.

Classification According to the current level of understanding of genetic material, genetic diseases can be divided into three major types of single-gene hereditary diseases, multi-gene hereditary diseases and chromosomal diseases.

A genetic disorder caused by a genetic abnormality in a pair of chromosomes from a father or mother in a homologous chromosome. Although there are many types of these diseases, more than 3,000 (see table [Number of diseases of single genetic diseases reported worldwide from 1958 to 1982], Number of diseases of single genetic diseases reported worldwide from 1958 to 1982), but The prevalence of each disease is low and most are rare. According to statistics from European and American countries, about 1% of newborns have severe genetic diseases. Single genetic diseases can be divided into four categories according to genetic methods: autosomal dominant genetic diseases. Of the 23 pairs of human chromosomes, one is related to sex and is called a sex chromosome, and the remaining 22 pairs are called autosomes. A pair of alleles on a homologous autosome is called a homozygote, and a pair of genes different from each other is called a heterozygote. If in the heterozygous state, the abnormal gene can also completely show a genetic disease, it is called an autosomal dominant genetic disease, such as multi-finger and multi-finger, congenital muscle rigidity. The occurrence of this type of genetic disease has nothing to do with gender. The prevalence is the same. One parent has the disease, and the child may develop in their children. It is estimated that about 7 per thousand newborns have often dominant dominant genetic disease. Autosomal recessive genetic disease. A genetic disease in which a pair of alleles on an autosome must be homozygous for an abnormal gene. Most congenital metabolic disorders fall into this category. Although both parents are normal in appearance, if they are carriers of a recessive gene that is often dominant, their children may still suffer from the genetic disease. Close marriage is easy to produce homozygosity, so the incidence of recessive genetic diseases in their children is also high. Autosomal incomplete dominant disease. This is a genetic disease that can and can only show symptoms to a certain extent when the abnormal gene is in a heterozygous state. Such as thalassemia, the abnormal gene causing the disease is homozygous, manifested as severe anemia, and heterozygotes are manifested as moderate anemia associated genetic disease. Divided into X-linked genetic diseases and Y-linked genetic diseases. The genes of some genetic diseases are located on the X chromosome, and the Y chromosome is too short, and there is no corresponding allele. Therefore, these abnormal genes will be transmitted with the X chromosome, so they are called X-linked genetic diseases. It is also divided into dominant and recessive. The former refers to a genetic disease that can be manifested by an abnormal gene on the X chromosome. Since a woman has two X chromosomes and a man has only one, the opportunity for a woman to obtain the dominant gene It is more common and the incidence is higher than that of men. However, there are only a few of these genetic diseases. Such as Xg blood type, and also anti-vitamin D rickets are X-linked incomplete dominant genetic diseases. X-linked recessive genetic disease refers to those who have an allele on the X chromosome only when they are homozygous. In women, the disease only occurs when a pair of alleles on both X chromosomes are abnormal. An X chromosome has a normal allele and would not have the disease. But men have only one X chromosome, but as long as the gene on the X chromosome is abnormal, they will show genetic diseases, so the incidence of men is higher than that of women. Such recessive recessive genetic diseases account for most of the associated genetic diseases, such as red-green blindness, hemophilia, etc. are more common. It is estimated that about 1 per thousand newborns have X-linked genetic diseases. The disease-causing genes of the Y-linked genetic disease are located on the Y chromosome, and there is no corresponding allele on the X chromosome. Therefore, these genes are transmitted between the next and the next generations along with the Y chromosome. Among humans, Y-linked hereditary diseases include hirsutism of the external auditory canal.

Polygenic inherited diseases are related to more than two pairs of genes. There is no dominant or recessive relationship between each pair of genes, and each pair of genes has a small effect alone, but each pair of genes has a cumulative effect. In general, polygenic hereditary diseases are far more common than single genetic hereditary diseases. Affected by environmental factors, different polygenic genetic diseases are affected to different degrees by genetic and environmental factors. The degree of influence of genetic factors on the occurrence of disease can be explained by heritability, which is generally expressed as a percentage. The higher the degree of heritability, the greater the influence of this polygenic genetic disease on hereditary factors. For example, cleft lip and cleft palate are polygenic genetic diseases, with a heritability of 76%, while ulcer disease is only 37%. Polygenic genetic diseases also include some diabetes, hypertension, hyperlipidemia, neural tube defects, congenital heart disease, and schizophrenia. In the population, the prevalence of polygenic inherited diseases is above 2 to 3%.

Chromosomal disease refers to a disease caused by abnormal numbers or morphology and structure of chromosomes. The incidence of chromosomal abnormalities in newborns is 0.5%. Chromosomal abnormalities are called chromosomal aberrations, and include autosomal and sexual chromosomal abnormalities. However, the proportion of chromosomal diseases in all genetic diseases is small, only about 1/10.

In the research and diagnosis of genetic diseases, there are several ways to determine whether a certain disease is genetic: research and analysis of pedigrees, analysis of clonic children, comparison of races, study of accompanying traits, animal models and DNA analysis. Through pedigree investigation, analysis, and comparison with the incidence of the population, not only can a disease be a genetic disease, but if it is a genetic disease, its genetic pattern can be further determined. Through the analysis of the incidence of monozygotic twins and siblings with twins, it is possible to determine the degree to which certain diseases are affected by genetic and environmental factors. The comparison of the incidence of different races and ethnic groups, especially the study of the incidence of different races in the same living environment may provide important clues for the judgment of genetic diseases. In the analysis of accompanying symptoms, the most commonly used is the same type of leukocyte antigen (HLA) system, which is used as a marker of genetic disease. Research as a genetic accompanying trait, and carrying out linkage analysis can also provide a basis for judging genetic diseases. At present, dozens of animal models of chromosomal aberrations and single-gene genetic diseases have been established, which provide a powerful means for the research of genetic diseases. DNA analysis is an important means of development in recent years. Among them, restriction fragment length polymorphism (RFLP) analysis is most commonly used in the diagnosis of genetic diseases.

Clinical diagnosis of genetic diseases is more difficult than other diseases. On the one hand, there are many types of genetic diseases, and on the other hand, the incidence of each genetic disease is low, so it is not easy for clinicians to gain experience in the diagnosis of genetic diseases. In addition to diagnostic methods for general diseases (such as medical history, physical examination, laboratory and instrumental examinations), the diagnosis of genetic diseases may also need to rely on some special diagnostic methods, such as chromosome tests, special biochemical determinations and genealogy analysis. The clinical manifestations of genetic diseases are the most important diagnostic clues. Each type of genetic disease has some symptoms and signs at the same time. It is called "syndrome". This is the first clue to prompt diagnosis. It is also the choice of laboratory tests and other genetics. The basis of scientific inspection. Patients with genetic diseases must inquire about family history in detail and draw accurate and reliable genealogy. The analysis of genealogy is not only a basis for diagnosis of genetic diseases, but also the identification of genetic methods and genetic counseling are extremely important. Dermatoglyphic analysis is another special method for the diagnosis of genetic diseases, which is most valuable for chromosomal diseases, and may also have some significance for other individual single-gene genetic diseases. The fingerprints, palm prints, palm folds, Finger prints and sole prints. The final diagnosis of many genetic diseases also depends on chromosome tests and special biochemical tests or DNA analysis.

Prenatal diagnosis is an important aspect of the diagnosis of genetic diseases. Amniotic fluid or villous tissue is obtained by puncture before the baby is born. Perform chromosome tests, specific enzyme activity or metabolite assays, or perform DNA analysis to determine the onset of the fetus and decide whether an abortion is needed to terminate pregnancy. This has the effect of reducing the birth of children with genetic diseases and improving the quality of the population. It is of great significance, especially under the condition that human beings can't effectively treat most genetic diseases at present, it is more significant to use termination of pregnancy to prevent the birth of children with genetic diseases. In recent years, due to the widespread application of B-type ultrasound scanners and the improvement of technology, it has great value in prenatal diagnosis, especially in the diagnosis of developmental deformities. Fetal scopes are also beginning to be used for prenatal diagnosis.

Genetic diagnosis is an important newly developed technology that can also make accurate diagnosis of nearly a hundred genetic diseases, but since most of these genetic diseases cannot be effectively treated, from the perspective of medical ethics, in addition to application In addition to prenatal diagnosis, the promotion of genetic diagnosis still has major problems.

For treatment and prevention, to cure genetic diseases, the defects that have occurred should be corrected at the level of genes or chromosomes. This method is called gene therapy and belongs to the category of genetic engineering. However, gene therapy still has great difficulties theoretically and technically, and currently it is not clinically applicable. The current treatment for genetic diseases is based on the premise of early diagnosis, by controlling environmental conditions (such as dietary components, etc.), regulating the metabolic process and preventing the emergence of symptoms, which is called "environmental engineering". Current treatments that can be applied to environmental engineering include diet control therapy (such as phenylketonuria fed with low or no phenylacetone yogurt powder), drug therapy (such as vitamin B6 for B6 dependence, allopurinol for gout, etc.), Surgical treatment (such as splenectomy for hereditary spherocytosis), enzyme supplementation (such as allogeneic bone marrow transplantation for Gaucher's disease), and symptomatic therapy (such as the use of antiepileptic drugs to control convulsions of phenylpyruvate). Although environmental engineering can reduce or eliminate the symptoms of some genetic diseases, it is beneficial to individuals, but the treatment results not only enable patients with disease-causing genes to survive, but also continue to reproduce offspring. If these patients do not experience Treatment could have been eliminated naturally, at least not for the offspring. Therefore, the impact of environmental engineering on the entire human race may be harmful, which will increase the frequency of disease-causing genes in the population from generation to generation, resulting in an increased incidence of genetic diseases.

Because there is currently no effective treatment for most genetic diseases, the prevention of genetic diseases is of special significance. Preventive measures include newborn screening, environmental protection, carrier detection and genetic counselling. Newborn screening is a simple test for a genetic disease in all babies born to start treatment before symptoms appear to prevent them from happening. Only those who can detect biochemical abnormalities before the onset of symptoms, and have treatments in place, and do not give genetic diseases that will cause severe disability in the future will be screened for newborns. Phenylpyruvate and congenital hypothyroidism are listed as statutory newborn screening programs in many countries. China has also conducted some screenings in Beijing, Shanghai, Tianjin, Wuhan and other places since 1982. Among them, phenylpyruvate screening in 12 provinces and cities published in 1985 is the first large-scale newborn screening in China. Biotinylase-deficient newborn screening is also a new topic internationally. China has started this screening in Beijing since 1987. Environmental protection refers to reducing or eliminating teratogenic agents, carcinogens, chromosomal aberration agents, and genetic mutation agents in the environment, mainly pollution produced in industrial and agricultural production. Carrier detection refers to the detection of individuals with normal appearance but with disease-causing genes or abnormal chromosomes from the population, to guide their marriage and fertility, and to prevent their genetic diseases in their offspring. The detection methods are mainly It is a chromosome examination, specific enzyme activity or metabolite determination, and DNA analysis. At present, it has been able to detect chromosomal equilibrium translocations and carriers of more than a hundred monogenic diseases, which is of great significance for the prevention of these genetic diseases. Genetic counseling first appeared in the United States in 1952, and was only launched in China after the 1970s. It is a medical staff to answer the genetic disease patients and their families on the etiology, genetic methods, prevention, and prognosis of the genetic disease, as well as to answer various questions raised And make estimates and give advice and guidance to the siblings of the patient's siblings. It can be considered that genetic counseling, prenatal diagnosis and termination of pregnancy are the "trilogy" to prevent the birth of patients with genetic diseases. Some people also include marriage counseling and fertility counseling in the scope of genetic counseling. These tasks are of great significance for eugenics and childcare.

Clinical characteristics of genetic diseases

1. Patients have special phenotypes (usually accompanied by mental retardation) and chromosomal abnormalities.

2. On the premise of removing the influence of environmental factors, there are patients in relatives, and the incidence is a certain proportion.

3. No patient appears in unrelated members (such as couples).

4, the patient has a specific age of onset, course characteristics and clinical manifestations.

5. In twins, the same disease rate of twins is higher than that of twins.

Genetic Disease Attachment: Introduction to Genetics

The research scope of genetics includes three aspects: the nature of genetic material, the transmission of genetic material, and the realization of genetic information. The nature of genetic material includes its chemical nature, the genetic information it contains, its structure, organization, and changes, etc .; the transfer of genetic material includes the replication of genetic material, the behavior of chromosomes, genetic laws, and the number of genes in the population. The realization of genetic information includes the original function of genes, gene interactions, the regulation of gene actions, and the mechanism of genes in individual development.