What is the n of chromosome?

Chromosome and chromosome-related diseases \x0d\ If the human genome is compared to a heavy book, this book consists of 23 chapters, each with its own story. Up to now, autosomes that have completed gene sequencing also include chromosomes 5, 6, 7, 9, 10, 13, 14, 16, 19, 20, 2 1 and 20. Chromosome diseases are characterized by large defects or duplication of genes, which make patients' intelligence and appearance development and even many organs of the body obviously abnormal, such as Down syndrome and microdeletion. \x0d\x0d\ New progress in genome sequencing research \ x0d \ Genome research represented by the International Human Genome Project is a "hot spot" in current biotechnology research. The completion of the draft human genome indicates a new era-post-genome era. At present, other animals that have completed genome sequencing include Caenorhabditis elegans (1998), fruit flies (2000), dogs (2004) and chickens (2004). China researchers independently completed the whole genome sequencing of rice, silkworm, chicken, blood sucking worm and other species. \x0d\x0d\ Clinical indications of chromosome examination \ x0d \ 1. At least 7%~ 10% of husbands with reproductive dysfunction such as infertility, repeated abortions and teratoma are carriers of chromosomal abnormalities. Common chromosomal structural abnormalities, such as balanced translocation and inversion, are abnormal in number, such as 45, XO caused by one less X chromosome or 47 XXXY caused by one more Y chromosome in women. Balanced translocation and inversion, because there is no gene loss, carriers themselves often do not get sick, but they can cause infertility, abortion, teratogenesis and other reproductive dysfunction due to chromosome abnormality of their germ cells. Abnormal number of sex chromosomes will not only lead to infertility, but also often lead to abnormal secondary sexual characteristics. \x0d\ x0d \ II。 Patients with abnormal secondary sexual characteristics \ x0d \ are mostly female. If they have primary amenorrhea, sexual dysplasia, short stature, cubitus valgus, shield chest and slightly lower intelligence, little or no pubic hair and armpit hair, low hairline, infertility, etc. , to consider whether they have X chromosome abnormalities. The common X chromosome abnormalities are Turner syndrome and circular X chromosome. Turner syndrome patients have one less X chromosome than normal women, and the karyotype is 45, XO. For some reason, patients with circular X chromosome break both ends of X chromosome at the same time and rejoin at the break. The smaller the ring chromosome, the more serious the clinical symptoms. Early detection of these abnormalities and appropriate treatment can improve the secondary sexual characteristics to some extent, and may also gain fertility. \x0d\\x0d\ III。 Patients with hermaphroditism of external genitalia \x0d\ For patients with unclear differentiation of external genitalia, such as penile hypospadias, clitoral hypertrophy is penis-like, and it is often difficult to correctly determine gender according to the appearance of external genitalia. Sex chromosome examination is helpful for diagnosis. According to the results of chromosome examination and other clinical examinations, hermaphroditism can be divided into true hermaphroditism, false hermaphroditism and sex reversal syndrome. \x0d\ 1。 True hermaphroditism: the internal genitalia is bisexual, that is, there are testicles, vas deferens, ovaries and fallopian tubes in the body at the same time. Chromosome examination shows two types: 1, 46, XX/46, XY, that is, there are two cell lines in an organism, and the proportion of each cell determines sexual orientation. The reasons are: X sperm and Y sperm are fertilized with two eggs at the same time, or X sperm and Y sperm are fertilized with eggs and polar bodies that have just formed and have not been excreted. 2. The karyotype is 46, XX, but some genes or fragments of Y chromosome are easy to locate on X chromosome, or autosomal genes are mutated to have the function of Y chromosome. \x0d\2。 Pseudohermaphroditism can be further divided into female pseudohermaphroditism and male pseudohermaphroditism. Female pseudohermaphroditism is characterized by female internal genitalia, including uterus, ovary and fallopian tube, and the chromosome examination is 46, XX. The internal genitalia of male pseudohermaphroditism is male, that is, the gonad is testis, and the chromosome karyotype is 46, XY. \x0d\3。 Sex reversal syndrome: that is, the karyotype is opposite to the phenotype, for example, the karyotype is female karyotype 46, XX, but the phenotype is like male; Or the karyotype is male karyotype 46, XY, but the phenotype is like female. 46. The main clinical manifestations of XX men are testicular dysplasia, cryptorchidism, hypospadias, little or no sperm, and possibly laryngeal whiskers. Axillary hair is sparse, and the incidence rate of the population is1/20,000. 46. The main clinical manifestations of XY women are tall, cord-shaped ovaries, no uterus, vaginal blindness, primary amenorrhea and underdeveloped breasts. \x0d\\x0d\ IV。 The chromosomal diseases of children with congenital multiple deformities and mental retardation and their parents are characterized by multiple deformities and mental retardation. The common clinical manifestations are small head, sparse hair, wide eye distance, low ear position, short neck, short nose, hypoplasia of external genitalia, cleft palate, hypotonia or hypertonia, epilepsy, palmoplantar perforation, anal atresia and figure. Chromosome examination can find abnormalities such as 2 1- trisomy syndrome. \x0d\ x0d \ v. Abnormal temperament \ x0d \ Tall, fierce and aggressive men, some of whom may be abnormal sex chromosomes. For example, in XYY syndrome, chromosome examination shows that there is one more Y chromosome than normal men, and the karyotype is 47, XYY. Most of the patients have normal phenotype, that is, they are healthy and often have fertility, but the male post-algebra is also 47, and the probability of XYY is greater than normal. The incidence of this disease accounts for 1/750 of the general male population. Men with slender figure, slender limbs, small penis, underdeveloped testicles and azoospermia may sometimes be accompanied by mental disorders. Chromosome examination is needed to determine whether they have Coriolis syndrome. Patients with this disease have one more X chromosome than normal men, and the karyotype is original 47, XXY. Its incidence rate is 65,438+0/800 in general men, 65,438+0% in mentally retarded men and 65,438+0/65,438+00 in infertile men. \x0d\ x0d \ VI。 People who have been exposed to harmful substances \ x0d \ radiation, chemicals, viruses, etc. Will lead to chromosome breakage. If the original fragment is not reconnected in the original position after chromosome breakage, various abnormal chromosomes will be formed, such as deletion, translocation, inversion, duplication, ring chromosome and so on. These aberrations, if they occur in somatic cells, will cause some corresponding diseases. For example, if they occur in germ cells, genetic effects will occur, affecting future generations, resulting in abortion, stillbirth and teratogenesis. \x0d\ x0d \ VII。 Premarital examination \ x0d \ Premarital examination can find abnormal chromosome carriers with normal phenotype, such as balanced translocation and inversion of chromosomes. The balanced translocation and inversion of chromosomes have normal phenotype because the genes are not lost, but they are easy to cause abortion, teratoma and stillbirth. Blind abortion will lead to an increase in the birth rate of deformed children. Premarital examination can also find that the phenotype is basically normal, but the sex chromosome is abnormal. These patients can show sexual dysfunction and infertility. Therefore, premarital examination is of great significance to prenatal and postnatal care. \x0d\\x0d\ VIII。 Patients with leukemia and other tumors \x0d\ Chromosome abnormalities of leukemia and other tumors can cause the expression of oncogenes in blood cells, leading to uncontrolled malignant growth of blood cells. Different leukemias often have their own characteristic chromosomal abnormalities, so chromosome examination is helpful for the diagnosis and prognosis of leukemia. \x0d\ 1。 Chronic myeloid leukemia: Ph chromosome is its marker chromosome, which is formed by mutual translocation of some fragments of chromosome 9 and chromosome 22. The appearance of Ph chromosome is a definite diagnostic index of chronic myeloid leukemia, and the appearance or disappearance of Ph chromosome during treatment can also be used as a reference index for curative effect and prognosis. \x0d\2。 Acute non-lymphocytic leukemia: Chromosome changes are mainly the reciprocal translocation of chromosome 8 and chromosome 2 1, and the reciprocal translocation of chromosome 15 and chromosome 17, forming four abnormal chromosomes and adding one chromosome 12. \x0d\3。 Acute lymphoblastic leukemia: Chromosome examination showed that chromosome 8 and 14 were translocated, chromosome 4 and 1 1 were translocated, and chromosome 9 and 22 were translocated to form 6 abnormal chromosomes and add an extra chromosome 2 1.