الفهرس 
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Abstract
The present work was carried out at the Nucleic Acids Research Department, Genetic Engineering and Biotechnology Research Institute (GEBRI), Mubarak City for Scientific Research & Technology Applications, New Borg El-Arab city, Alexandria, Egypt.
The present study was conducted to detect the relatedness and diversity between four sheep breeds in Egypt. Randomly amplified polymorphic DNA (RAPD) assay and Restriction Mapping techniques for 18S rRNA gene were used in this study to detect such relationships. This is considered to be the first step for planning advanced breeding strategies to improve the production of such breeds.
Four Egyptian sheep breeds (Barki, Ossimi, Rahmani and Romanov)were used in this study. These breeds were obtained from different localities (Kilo 59, desert Road, Alexandria, Sakha, Kafer Elsheikh and Mehalet Mousa, Kafer Elsheikh). Ten blood samples were collected from each breed for DNA extraction.
RAPD technique was performed using 16 random primers ranged from 10- 20 base pair.
The sum of amplified fragments for all primers were 139 bands, the highest number of amplified RAPD fragments were 123 bands in Ossimi, 122 bands in Barki, 121 bands in Rahmani and 113 bands for Romanov.
RAPD analysis showed genetic similarity among the four sheep breeds as: 90% (Barki x Ossimi), 87% (Barki x Rahmani), 87% (Ossimi x Rahmani), 80% (Ossimi x Romanov), 80% (Rahmani x Romanov) and 74% (Barki x Romanov). The highest genetic similarity observed between Barki and Ossimi (90%), while the lowest was between Barki and Romanov (74%).
PCR-RFLP technique was also used for estimating genetic similarity among these four breeds. PCR products generated from 18S rRNA gene amplification (600 bp) were digested with various restriction endonucleases (Aval, AluI, Apal, AatIl, BamHI, Cfol, Cail, EcoRI, EcoRV and Hinfi). Three out of these ten enzymes digested the amplified 18S rRNA gene product. Restriction Mapping for 18S rRNA analysis showed that there was no genetic diversity among these four breeds.
In conclusion the results of the present work revealed the effectiveness of RAPD markers in detecting enough polymorphism between sheep breeds to determine their genetic relationships. Furthermore, the RAPD technique can be used as supporting marker for taxonomic identification in sheep. The Romanov sheep breed was the most divergent genotype from all other genotypes. These wide variations of Romanov breed
allow for future research to improve sheep breeding in Egypt. On the other hand the Restriction Mapping for 18S rRNA gene did not produce any genetic polymorphisms between the studied sheep breeds so, this technique was not useful in detecting the diversity between breeds based on 18S rRNA gene in this study.