Inheritance and genetic diseases

Bookmark and Share
The same or similar physical characteristics (such as hair color, disease) or psychological characteristics that occur with ancestors and descendants can be inherited by the children.

Operation
At the core of every human cell are densely packed information on the blueprint of every human individual and the workings of his body. The blueprint of the entire human genome, the genes are stored in every human cell. Approximately 100,000 genes are strung on the chromosomes. In normal human somatic cells, the genes are distributed on 46 chromosomes, which arrange themselves in pairs. One chromosome of a pair comes from the mother, the other from the father. 22 pairs, the autosomes are equal in men and women. The 23rd Pair of chromosomes, the sex chromosomes (sex chromosomes), determine the sex of the people. The female Gonosomenpaar consists of two x-shaped chromosomes, one from the male X chromosome and one Y chromosome.

Thus contains the future living in the union of egg and sperm cells also only 46 chromosomes, the germ cells make during their maturation through a so-called reduction division, the number of chromosomes is halved. Thus, all egg and sperm at fertilization only 23 chromosomes.

The female germ cells are all equal. In male germ cells, however, there are sperm with X chromosomes and others with Y-chromosomes. The sex of a child is dependent on what comes of sperm for fertilization. Blend meets a Y chromosome to the oocyte, the facility is being built for a boy growing oocyte and X-chromosome, a girl (see illustration above).

The nuclei of women always contain two X chromosomes, one inherited from the mother and the other from the father. Nuclei of men contain an X chromosome, inherited from the mother and one Y chromosome, inherited from the father (see left). The entire genome, with the exception of sex chromosomes in males, is thus doubled.

Genetic Diseases
Certain deviations from the regular structure, in the shape and number of chromosomes, interfering with the blueprint of the cell and cause serious diseases. The predisposition to certain genetic diseases occur quite frequently, while others are very rare. A genetic disease may already occur during early embryonic development spontaneously or having been passed on from one parent to the offspring be. Many genetic diseases manifest themselves early in life, others only very late.

If there is a change in a gene or an altered gene is inherited from our ancestors, there is usually still a healthy copy of the second autosome. How diseases are inherited, whether by contact or pass on the disease "only" as an investment, depends on whether the characteristics of dominant or recessive inheritance.

If in a family known cases of a disease that can be inherited, is sought by means of genetic analysis in the parents or the child after the altered gene. Before a genetic analysis of the genetic parents are advised by a specialist.

There are also chromosome damage, which is not inherited, but occur due to faulty cell division concluded. With few exceptions, are not consistent with chromosomal damage and lead to life - with a few exceptions - usually early in the pregnancy to abort. The best-known chromosomal defect that occurs due to an incorrect division of chromosomes is reached, the Down's syndrome.

The World Health Organization estimates that up to five percent of the world population are affected by genetic diseases.


Dominant / recessive inheritance

The same or similar physical characteristics (such as hair color, disease) that occur with ancestors and descendants, but also psychological traits or diseases can be inherited. The entire genome is duplicated cells in the body - with the exception of sex chromosomes in males.

Backup in the chromosomes
If there is a change in a gene or an altered gene is inherited from our ancestors, then there is usually still a healthy copy on the second chromosome. Nevertheless, under certain circumstances, a disease is inherited. There are diseases that occur in each case to the outbreak, other diseases, however, the carrier can pass on to their children, without even getting sick. How diseases are transmitted by contact and whether the diseases or inherited "only" as an investment depends on whether the characteristics are inherited dominant or recessive.

    Dominant traits always occur in appearance.

    Recessive traits are masked by dominant characteristics, but sometimes occur through inheritance more apparent.

A defective recessive gene is usually obscured by a dominant. However, both parents are carriers of a recessive hereditary disease with every child a chance that both recessive genes inherited from both or neither. In addition, the child can pass the defective gene on to his own offspring.

Exceptions to the sex chromosomes
If a defective gene that causes a disease on a sex chromosome, there are exceptions to the dominant or recessive inheritance ways: If the feature is located on the Y chromosome, the disease occurs in all cases and are inherited, since in the cells are no other Y-chromosome.

Is a boy, a defect on the X chromosome before, such as in Duchenne muscular dystrophy, it must come the defective X-chromosome of the affected boy from the mother because the father he has inherited the Y chromosome.

Rules in the hemophilia
Hemophilia is an X-linked recessive inherited bleeding disorder. The health of the mother (= a carrier) derived feature occurs in 50% of the children, but with no daughter (of which 50% are female carriers) in appearance. For women, the feature is visible only when the gene is present on both X-chromosomes. Hemophilia is inherited through the non-sickening women (female carriers) to the hemophiliac on the sons.

In the X-linked dominant inheritance of the trait is always father to his daughters, but never transferred to his sons, because the X chromosome in males always comes from the mother.

{ 0 comments... Views All / Send Comment! }

Post a Comment