الفهرس 
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Abstract
The differences in genetic integration between three natural populations of
D.melanogaster were studied in a series of experiments. The populations were collected
from widely separated localities in Egypt and Libya. The collection sites of the natural
populations represent the two localities (Alexandria and Sewa) from Egypt and one locality
(Bani-Walid) from Libya.
In one of these experiments, quantitative and qualitative differences in chromosomal
polymorphism between the different populations were examined for each population.
Salivary gland chromosomes of the larvae obtained from the wild collected females were
cytologically examined for the chromosomal inversions which they contain.
In the other, experiments, the performances of these populations with respect to some
of the fitness components were compared with that of the F1 and F2 of the crosses between
them. Three characters were studied, whose behavior could be reasonably related to fitness,
under different environmental conditions. These characters were body size; average daily
egg production and the length of development time. In one of these series, the crosses were
carried out between the three widely separated geographic populations. The comparisons
were carried out at the three different temperatures 15°, 25° and 29°C.
The results obtained from these experiments can be summarized as follow;
1- A total of eight different cosmopolitan Inversions were detected. These inversions were
(2R)NS, (2L)Cy and (2L)NS on the second chromosome and (3R)P,(3R)C and
(3R)Mo,(3L)P and (3L)M on the third chromosome.
2- The X-chromosome and the fourth one were totally free of any inversion.
3- Three simple inversion associations between two of these inversions were detected in
Alexandria populations. These associations were between In( 3R )P and In(3R)C, In( 3R )P
and In(3R)Mo and between In( 3L )M and In(3L)P in Alexandria population.
4- The amount and the frequencies of the different chromosomal inversions varied from one
population to another. All of these inversions were found in Alexandria population while
some of these inversions were absent in Sewa and Libyan populations.
5- The distribution of inversions among individuals of the different populations indicated
that the Alexandria population is highly polymorphic than Sewa and Libyan populations.
The differences in the degree of polymorphisms were attributed to genetic and ecological
differences between populations.
6- The crosses between the three different widely separated geographic populations
indicated that genetic variations are responsible for differences in body size between these
different natural populations. At the three different temperatures, the wing and thorax
lengths of all crosses exceeded the mid-parent values and that was accompanied with low
variability among individuals. The hybrids of the two traits were inferior to the mid-parent
levels and had higher variability than that level.
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