الفهرس 
GENETIC IMPROVEMENT OF FERTILITY TRAITS IN SHEEP USING MARKER-ASSISTED selectIONOnly 14 pages are availabe for public view
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Abstract
The present work was carried out at Nucleic Acid Research Department (NAR), Genetic Engineering & Biotechnology Research Institute (GEBRI), City of Scientific Research & Technological Applications, New Borg El-Arab, Alexandria.
Improvement of fertility trait in farm animals, especially for small ruminants such as sheep, has become desiring interest. This can be achieved by improving the genetic worth of the stock by proper selection methods for improving reproduction rate and production efficiency. The present investigation had been carried out for revealing FSHR gene polymorphisms in Ossimi sheep breed under Egyptian conditions, looking for association between fertility trait and FSHR gene variants and detection of SNPs associated with high litter size production.
The objective of the present study has been achieved by employing different molecular genetic techniques, such as polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) and DNA sequencing.
However, blood samples from fifty selected Ossimi sheep (20 high and 30 low fertile animals) were collected in tubes containing an antiagulant tripotassium EDTA and then DNA from these samples were extracted for amplifying FSHR gene using PCR which yield a fragment of 250-bp. Single stranded conformational polymorphism (SSCP) of amplified fragments for FSHR gene showed two genotypes: AA genotype (homozygous) and AB genotype (heterozygous). The AA genotype is the most frequent genotype in high fertile animals.
DNA sequencing of fragment of FSHR gene (250-bp) revealed nucleotide sequence variation among high and low fertile animals. Where, the results showed that six SNPs (G/71, G/72, G/77, A/110, A/111 and A/191) were detected in three high fertile animals (2, 4 and 16). While, ten SNPs (T/1, C/2, T/14, A/69, A/70, A/71, A/74, G/74, A/75 and A/136) were found in five low fertile animals (24, 25, 26, 28 and 41). Consequently, FSHR gene can be used as marker-assisted selection (MAS) for high fertility trait in Ossimi sheep according to the previous SNPs markers in FSHR gene which may be useful in genetic improvement for fertility trait in Ossimi sheep. In contrast, the previous SNPs markers in low fertile animals can be forbidding in breeding programs for fertility trait in Ossimi sheep.
Statistical analysis (LSM) revealed that no significant effects for season and parity on litter size in Ossimi sheep, while, the significant effect was only found for age. Breeding value were calculated and divided the fifty animals into two groups; high breeding value animals (good parent in breeding programs) and low breeding value animals (forbidding parent in breeding programs). T-test analysis showed no significant differences between means of the two genotypes (AA and AB) in Ossimi sheep.
The results of this study concluded that FSHR gene in Ossimi sheep moderate polymorphic and maybe it is the major gene which affects prolificacy in Ossimi sheep. The association of polymorphisms of FSHR gene (exon 10) with fertility can be used as a molecular breeding marker in Ossimi sheep. Low fertile sheep mostly had SNPs at beta peptide, which conform extracellular and intercellular part of receptor, which important in binding of FSH and transport of the signal of hormone. While, all SNPs in high fertile animals were in helical part of receptor which not affect directly the binding of the follicle stimulating hormone. However, large number of animals is required for detecting enough FSHR polymorphisms associated with fertility trait in Ossimi sheep using molecular genetic markers (SSCP-SNPs).