REPRODUCTION_CROISSANCE

Important: The translations are performed by google. Thank you to forgive the shortcomings that still will understand much of the content of the page. Thank you for your understanding.

The site contains about 1000 pages! Each of them will be translated, which requires a lot of patience and understanding. Thank you very much.

The life cycle is repeated indefinitely, from generation to generation. Human beings are born, grow, reproduce and eventually die. The steps that lead from the fertilization of an egg by a sperm until full development of an adult individual, is one of the most spectacular demonstrations of detailed complexity of natural processes.

The life of every human being is conditioned over the years by a variety of factors more or less unpredictable. If genes inherited from the parents are crucial in many respects, their role remains to a large extent, limited the field of potential, he gives free rein to the game experience and chance. What is genetic traits can be profoundly altered by the environment, living conditions (diseases, food, education, social context), which contribute to the achievement of specific individual. The maximum size, for example, is in its genes. But if he does not receive a proper diet during childhood, he may never get there.

Longevity, such as size, also depends on genetic factors. But again, the physical environment and the social environment exert a dominant influence, as evidenced by the increase in life expectancy in industrialized countries during the last hundred years. In France, a century ago, life expectancy was 50 years, and now it is nearly 79 years for women and 71 for men. We thus gradually approaching our genetic potential for longevity, which is about 90 years. As for maximum life expectancy, it is estimated at 115 years, although this age can be exceptionally exceeded. This increase in average longevity is due to a number of concurrent factors, mainly related to changes in lifestyle. Hygiene, both public and private, and medical advances are important, as well as the improvement of working conditions and food.

Children resemble their parents, but always with differences. Genes, made up of DNA, determining the size, the color of the skin, hair and eyes, facial features, etc.. We inherit from our parents, which explains the similarities that occur in the same family for generations. This is the moment of fertilization that is passed this genetic heritage, half from the father's sperm, and the other from the mother's egg.

In each cell of the body, genes are carried by 46 chromosomes arranged in 23 pairs, 22 pairs of non-sex chromosomes or autosomes and one pair of sex chromosomes and sex chromosomes. The set is the KARYOTYPE, whose study will detect any abnormalities or genetic diseases. One of each pair of chromosomes is a replica of a maternal chromosome and the other with a paternal chromosome. The genes responsible for specific functions, are in specific chromosomal locations of their support, always with two copies of the same gene, one on each chromosome of a pair.

These two genes may be identical or different, which affects the characteristics of the individual. A dominant gene is one that plays a key role, even if it is associated with a different type of gene, said recessive. It is only when the same recessive gene is present on each chromosome of a pair, it may be the case.

BOY OR GIRL? The sex of an individual is determined at the time of fertilization of the ovum mother, a father's sperm. Women have two X sex chromosomes, while males have one X and one Y. Thus, only the nature of the sperm fertilizing, which determines the sex of the unborn baby. All eggs from the mother have only X chromosomes In contrast, half of the sperm chromosomes are X and Y chromosomes in half

If it is an X sperm that fertilizes the egg, the embryo that will result will be XX, ie female. If it is a Y sperm, the embryo will be XY, ie male. The fact that the X and Y chromosomes are equally distributed in a population of sperm, why, statistically, there are almost as many men as women.

OUR POTENTIAL IS HEREDITARY TO THE COMPLEX MOLECULES THAT GOVERN OUR DEVELOPMENT AND ALL OUR EXISTENCE.

All necessary instructions are contained in the nucleus of every cell in our body. They are listed there as GENOA on giant molecules DEOXY-RIBONUCLEIC or DNA ACID.