The inheritance is the acquired organic similarity
of the ancestors (transmission of the characters of the ascending
ones to the descendants). The genetics is the science that takes
care of the study of the inheritance tries to clarify the nature
of the genetic material transmitted the descendants, as the transference
of this material takes place and as they are the processes that
assure the material accomplishment the characters.
From the babylonian and Syria civilizations one
knew that the characters are transmitted of ancestors to descendants.
After Aristotle still the mechanism was not known transmission.
During centuries XVII and XVIII certain preform investigators indicate
that the new being or is preformed in the egg or the gametics. Later
they saw that this was not certain because when studying the gametics
verified that they were masses of protoplasma uniforms, others indicated
that there were external mystical forces that caused the development
of the egg. From the average age to century XIX the inheritance
was studied by breeders of animals indicating that of the union
of two ancestors they appeared descending with intermediate characteristics
to the ancestors and they called hybrids, its followers were known
like hybridists. Kolrenter studied the characteristics of the hybrids
comparing them with the ancestors found that: the hybrids not always
were of intermediate characteristics, that determined characteristics
disappeared in hybrids but they appeared in his descendants.
Father of the genetics, discovered the basic mechanisms
of the inheritance, studied the plant of the pea through different
a) Selection of a variety of pure line for each
character: Red x Red : 100% red
b) I cross plants that were different in a character
being pure lines, Smooth x Rough : 100% smooth one; these could
as well be crossed giving Smooth x Smooth : 25 % rough and 75 %
c) I cross lines of plants that were different
in two characters, tall-Rojas X Small-White: 100% red and tall;
when crossing itself between tall-red x tall - Red: red tall, high
white, small red, small white. In order to explain this it defined
the hereditary units that appear by pairs and each one will be the
person in charge of a character.
Laws of the inheritance
Law of the segregation; the hereditary units exist
by pairs in the individual during the formation of the gametics
these separate and each one will go to a gametic, of this form each
single gametic has a unit of each type.
Law of the combination; the distribution of each
pair of the hereditary units is independent of the distribution
of other pairs.
Parenteral generation, is the first generation.
F1; first filial generation. F2; second filial generation. Phenotype,
physical appearance that is from the activity of a pair of genes.
Both genes that control a characteristic represent by a pair of
letters, one is dominant which masks the action of the recesiv.
Genotype, set of all the genes of an alive being. Individual homozygote,
the one that both has genes that determine. Individual character
heterozygote, the one that both has genes that determine a different
character alleles, genes that are in opposition monohybrid crossover,
crossover in which is present solely a pair of allele dihibrid crossover,
crossover in which are present two pairs of alleles
Cytological base of the inheritance
The hereditary units must have relation with the
chromosomes, after Mendel was discovered the conduct of the chromosomes
during the gametogenesis. The chromosomic theory arises from the
propose inheritance by Sutton (1902), the genes are in the chromosomes
and they are transmitted to the descendants during the gametogenesis.
Most of hereditary factors depends on the genes
which are in the chromosomes. In many cells units exist that reproduce
in the cytoplasm and they are in him transmitting itself of generation
in generation, to these units is called plasmogenes, plasmones to
them or plásmidos. During the mithosis the plasmids ones
are divided in halves and each part goes to a certain cell, all
do not have the same information but she is practically identical.
How it is the prediction of results in the genetic crossovers? Examined
the data we can predict the results. The possible genotypes are
based on the combinations that are possible with the types of gametics.
Punnett I devise the diagram or chessboard of Punnett. These are
the awaited data but that they do not have to agree with the observed
ones, speech of probabilities. Action of the genes. It is accepted
that each gene exerts a specific action and any change in its structure
is going to produce consequences at level of alteration in the activity
of the lost gene and of the activity of the gene.