B, Gahne

Genetics Selection Evolution

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Gahne B

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Immunogenetics: a review and future prospects

B Gahne

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B. GAHNE

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IMMUNOGENETICS: A REVIEW AND FUTURE PROSPECTS

proposed to account for this disappearance of the intragenic regions during the process of trans-
cription or shortly afterwards is that both the intragenic and expressed sequences are first trans-
cribed into a precursor mRNA (HnRNA). After that the inserts are excised while the released
coding regions are spliced to from the final active mRNA. Specific enzymes are responsible
for this processes.
According to speculations on the possible function of the intragenic sequences the most
probable alternative is that they have some control function in the regulation of protein synthe-
sis (MARX, 1978).
The new model of " the gene in pieces " gives rise to some interesting aspects on the origin
of genetic variation.
First, moderately repetitive sequences within the intragenic regions are supposed to be
sites where recombination through crossing-over frequently occurs (GILBERT, 1978). Obviously,
such recombinational events would change the base sequences of the intragenic regions of DNA
(outside the repetitive sequences) as well as the order between the expressed regions. Thus,
these changes within the gene would be comparable with some sort of major mutations. If such
within-gene rearrangements are not rare they should be a tremendously rich source of new gene-
tic variation in a heterozygous population. In fact, they could for instance easily explain (I)
why selection in such a population can result in strains which after a number of generations trans-
cend the limits of variation in the original population, or (2) why crossing of two different lines
after they have reached a selection plateau can give rise to new genetic variation for selection to
work on.
The recombinational changes of the intragenic base sequences of DNA would, in accordance
with the earlier assumptions, give rise to changes in the rate of protein (enzyme) synthesis by
regulation of the rate of transcription while the changes of the order between the expressed regions
would generate new combinations of polypeptides coded by these regions.
Consequently, eukaryotes would be able to develop new, complex functions faster than
prokaryotes without any need of increasing the rate of mutations in already existing base sequences
(DOOLITTLE, 1978).
In animal breeding selection has mainly been focused on increasing the rates of synthesis
of various products suitable as food like milk, eggs and meat. It seems therefore natural to
assume that these improvements have been brought about by increasing the rates of synthesis
of those enzymes which are responsible for catalyzing the reactions involved in the production
processes referred to. If this is true, the variation caused by differences among the controlling
genes should constitute the main part of the genetic variation exposed to artificial selection.
IMMUNOGENETICS: A REVIEW AND FUTURE PROSPECTS
B. GAHNE
Departement of Animal Breeding and Genetics
Swedish University of Agyicultua  Sciences, S-75007 Uppsala, Sweden
The following areas of immunogenetics are briefly reviewed: red cell and histocompatibility
antigens, immune response genes, general genetic immune responsiveness, allotypes and immuno-
deficiencies. The emphasis is placed on basic principles and on farm animals. Some applica-
tions and future prospects within the field of immunogenetics are also discussed.
MOLECULAR APPROACH TO QUANTITATIVE INHERITANCE
M. GILLOIS, C. CHEVALET A. MICALI
Laboratoire de génétique cellulaire
Centre de Recherches de Toulouse, T’.!V.Ti’.!.,
B.P. 12, 3z 2o Castanet, Tolosan, France
Two main ideas are considered: genes do not work independently, but according to one or
many ordered sequences as in metabolic pathways; and genes code for sequential molecules whose
main property is to enter into stereospecific associations, involved in enzymatic catalysis and in
regulation mechanisms. Quantitative effects and interactions of genes are defined as resulting
from the dynamical processes attached to biochemical networks. First results about one enzy-
matic step are quoted, and discussed with respect to their relevance to quantitative inheritance.


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Immunogenetics: a review and future prospects

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