A detailed explanation of human trisomy 21! 5

Autosomal dominant disorders caused by autosomal mutations.

Trisomy 21, also known as congenital stupidity or Down syndrome, is the most common birth defect caused by autosomal aberrations in children. As the name suggests, the disease is an intellectual disability with a specific phenotype caused by congenital factors. The incidence of trisomy 21 in live births in our country is about 3 2, and 60% of children with live births die in the early fetal period.

The main clinical features of the child are intellectual disability, physical retardation, and special facial features, which may be accompanied by multiple malformations.

It is the three-body problem. Our high school teacher taught Oh, I just graduated, and I'm still more impressed, I hope it can help you... I've been making sentences for a long time, and I can only explain it to this extent...

Trisomy 21, also known as congenital stupidity or down-syndrome, is an autosomal aberration and is one of the most common chromosomal diseases.

1.**。May be related to the following factors:

Maternal bush stockings are associated with advanced gestational age, multiple births, pregnancy after years of infertility, viral infections in the early stages of pregnancy, use of certain chemical drugs and radiation exposure, endocrine disorders, and genetic factors. The above factors can cause the aberration of chromosome 21 in somatic cells in sick children, that is, the 21st pair of chromosomes is trisomy, so it is called trisomy 21.

2.Clinical presentation.

1) Special dementia facies. The head is short, the neck is short and wide, the occipital bone is flattened, the teething is delayed, the nasal bridge is flattened, the distance between the eyes is wide, the ocular cleft is small, the epicanthal folds are low, the lateral canthus is high, nystagmus, and occasionally cataracts. The palatal arch is high, the mouth is half-open, the tongue often sticks out of the mouth, salivating profusely, and tongue fissures can be seen in older children.

2) Backward mental and physical development. It becomes more and more pronounced with age. Mental and motor development are delayed, sitting, standing, walking, and language are significantly backward than normal children, pronunciation is not clear, expression and calculation skills are worse, and attention is poor, but the temperament is gentle and quiet.

Most of the children are moderately mentally low, and a few are mildly low, and their physical development is also backward compared with normal children, and their sexual development is delayed.

3) Characteristics of limbs. The muscle tone of the limbs is low, **delicate, the palms and soles of the feet are often perforated, the hands are wide and thick, the joints are soft and can be overmoved, the little finger is short, the end is often bent inward, the second phalanx is often underdeveloped or absent, and the distance between the big toe and the second toe is widened. Bone age lags behind normal, and short stature.

4) Miscellaneous. Immunocompromised, susceptible to respiratory tract infections and dissipation and intensification system dysfunction, in addition, often complicated by a variety of congenital malformations, the incidence of leukemia is also higher than that of the general population.

3.Diagnosis. It can be considered based on the characteristics of the special face, low intelligence, striated characteristics, and delayed physical and motor development, but chromosomal examination is required to confirm the diagnosis.

Patients with atypical symptoms need to rely on karyotyping to confirm the diagnosis. Its karyotype is mostly 47,xx (or xy),+21.

Answer]: B Down syndrome, also known as trisomy 21 and congenital stupidity, is an autosomal aberration, which is the most common type of chromosome disease, which is caused by a small G group chromosome in the patient's cells, that is, chromosome 21. According to karyotype analysis, children with Down syndrome can be divided into three types:

Standard, translocate, chimeric type. Among them, the standard type is the most common, with 47 somatic chromosomes and an additional Chrysan's chromosome 21, with a karyotype of 47, xx (or xy), 21.

The karyotype of both parental peripheral blood lymphocytes is normal.

Answer]: E chromosome examination is the basis for the diagnosis of this disease, and it is also the main basis for classification. Therefore, choose e. Test site: Poor cytogenetic diagnosis of 21-33 Qingfeng syndrome.

Mental retardation: There are varying degrees of intellectual developmental disabilities. Growth retardation:

Delayed physical and motor development, short stature, backward bone age, bare hands older than chronological age, late teething and abnormal order; The limbs are short, the ligaments are lax, and the joints can be excessively flexed; low muscle tone, abdominal distention, may be accompanied by umbilical hernia; The fingers are thick and short, the little finger is particularly short, and the middle phalanx is short and broad, curved inward.

Answer]: Trisomy C21 (also known as congenital stupidity or Down syndrome) is a chromosomal aberration of the common limb and is the most common type of chromosomal disease. The older the mother, the higher the incidence of the disease.

The child has a peculiar facial appearance: wide eye distance, small eye fissure, and lateral slanting of the eye. The base of the nose is low and flat, the outer ear is small, the hard palate is narrow, the tongue often sticks out of the mouth, and there is a lot of salivation.

**Texture features: through the hand, the ATD angle increases; The first refers to an increase in the number of radial baskets; The hallux toe is arcuate on the side of the tibia, and the 5th toe has only one finger fold.