In a school course of biology, in high school you for certain got acquainted, or still will get acquainted with genetic tasks. Genetics - very interesting science. She studies regularities of variability and heredity. Representatives of any of species reproduce similar to. However there are no identical individuals, all descendants to a greater or lesser extent differ from the parents. The genetics as science, gives the chance to predict and analyze transfer of hereditary signs.
Instruction
1. For the solution of genetic tasks use certain types of a research. The method of the hybridological analysis was developed by G. Mendel. It allows to reveal regularities of inheritance of separate signs at sexual reproduction of organisms. The essence of this method is simple: in the analysis of certain alternative signs their transfer in posterity is traced. Also to be carried out accurate accounting of manifestation of each alternative sign and the nature of each certain individual of posterity.
2. The main regularities of inheritance were also developed by Mendel. The scientist output three laws. In a consequence they and were called - Mendel's laws. The first is a law of uniformity of hybrids of the first generation. Take two heterozygotic individuals. When crossing they will give two types of gametes. The posterity at such parents to appear in the ratio 1:2:1.
3. The second law of Mendel is a law of splitting. at the heart of his statement that the prepotent gene not always suppresses recessive. In this case not all individuals among the first generation reproduce signs of parents - the so-called intermediate nature of inheritance appears. For example, when crossing homozygous plants with red flowers (AA) and white flowers (aa) the posterity with pink turns out. Incomplete domination quite widespread phenomenon. It meets also in some biochemical signs of the person.
4. The third law and the last - the law of independent combination of signs. Manifestation of this law requires observance of several conditions: there should not be lethal genes, dominance has to be complete, genes have to be in different chromosomes.
5. Tasks in genetics of sex stand alone. Distinguish two types of sexual chromosomes: X-chromosome (women's) and Y-chromosome (men's). A floor having two identical sexual chromosomes is called gomogametny. The sex defined by various chromosomes is called geterogametny. The sex of future individual is defined at the time of fertilization. Sexual chromosomes, besides the genes bearing information on the field contain also others, not having any relation to it. For example, the gene which is responsible for blood clotting bears female X-chromosome. The signs linked to a floor are transferred from mother to sons and daughters, from the father - only to daughters.