Theoretical basis of inbreed strains

Hardy-Weinberg Principle

 Hardy-Weinberg Equilibrium

Firstly, some basic genetics must me understood. Alleles refer to genes that codify for the same trait or protein product, but have a different sequence (say, gene A and gene B are different but codify for the same thing).

Now, the probabilities of each allele are different (to simplify certain conditions, non-common cases are omitted); generally speaking, one comes from the mother whilst the other comes from the father. As such, the probability is established as follows: A+B=1; the combinations for the alleles can be the following: AA, BB or AB. Doing the sum of the probability of the combinations, the following binomial distribution is established:

A2+2AB+B2=1

The latter equation, however, has certain limitations; to which the Hardy-Weinberg equilibrium is established.

The population contains an “infinite” amount of individuals

There is no genotype that influences in mate choice

There are no mutations or natural selection

No migration both in or out of the populations

Physical conditions of all present individuals are equal

The primary objective is to avoid the AB trait mice, and instead obtain either AA or BB; which at this moment will be referred to as low trait and high trait respectively. For this to occur, there has to be a definition for inbred strain.

Inbred strain

In other words, there is a loss of AB genes present in mice after multiple generations of breeding. The coefficient of inbreeding (F) is observed by the following equation (in which i refers to the initial generation of AB genes while c is the generation of AB genes after x generations):

Eventually, after approximately 20 generations; there is very little heterozygosity (AB genes) within the mice.

The benefits of such conditions are that a breed of mice can be “created” without the disturbance of a variety of conditions; the entire process is practically controlled from start to finish and the results obtained are very favorable.

Development of models

Two way artificial selection can be used to crate low and high lines widely different for a trait from which inbreed strains can be hence produced. To make a general approach to selection, its procedure begins in a selective breeding by measuring the trait of interest in a large founder population that has wide genetic heterogeneity. At each subsequent generation, progeny are phenotyped and selected as the best for that trait and bred to create the following generation. This is repeated until the change in the population mean produced by selection response plateaus, which normally determines exhaustion of additive genetic variance for the trait.

The degree of heterozigosity can be increased above the random bred by generating contributions from each family more equal that can be achieved by tang the best female and male from each mating and using them as parents in the next generation.

Sergio Iván Zamudio Quevedo A01163304 Mario Alfonso Arenas García A01162581

IntroductionLaboratory mice have a variety of functions; they are generally used for the research of diseases; from initial manifestation to the possibility of the synthesis of a cure. On the other hand, some mice require certain qualities or traits needed for the research; such as muscular mass, cardiac condition, certain genes in their DNA, etc. For such traits, selective breeding is used in order to “achieve” such mice.

References: Whushaw, Ian Q. & Kolb, Bryan (2005). The behavior of the laboratory rat. Oxford University Press, New York.

ConclusionsThe practicality of such conditions can be considerably useful when doing hereditary studies when involving identical alleles. For instance, a study in which the entire population needs to have hypertension can be achieved considering the conditions established previously mentioned; allowing an easier study for the disease and its peculiarities. On the other hand, (and taking on basis the example mentioned throughout the work) a species with "superior" qualities can be obtained; to which they can be used for a variety of things.

The main point of this is to be able to control the hereditary conditions of the populations to achieve a certain end objective, that is to be able to "replicate" mice with certain physiological characteristics, explain the hereditary conditions to which a disease can appear, amongst other matters.