الفهرس 
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Abstract
This chapter was carried out to investigate possibilities of
utilizing molecular genetics for genetic improvement of growth
performance in Egyptian Barki and Rahmani sheep. Discovering and
genotyping some single nucleotide polymorphism (SNPs) as a method of
molecular genetics was the objective of this chapter.
A total of 74 Barki and 74 Rahmani lambs of both sexes, born in
the period from 2013 till 2015 were included in the study. Barki and
Rahmani lambs were selected from Borg Al-Arab and El-Serw research
farms, belonging to Animal Production Research Institute (APRI),
respectively. Blood samples were collected from the jugular vein into
ethylene diamine tetra-acetic acid (EDTA)-containing vacutainer tubes.
The body weights of all individuals were recorded monthly from birth till
eighteen months of age. Individual estimated breeding values (EBV) for
twelve-month body weight were estimated using random regression
model. Individuals with the lowest and highest EBV were selected from
both Barki and Rahmani males and females to determine LEBV (24 Barki
and 20 Rahmani) and HEBV (23 Barki and 20 Rahmani) groups,
respectively. Genomic DNA was extracted from blood using the salting
out extraction method. A total of nine candidate SNPs were selected
according to individual-based on coefficient of genetic variation (Fst
values) and the genes that have possible association with growth
harboring those SNPs of previous study on Barki lambs (Kim et al.,
2015). Allele Specific Polymerase Chain Reaction (AS-PCR) was used
for genotyping in both breeds. One-way ANOVA, in the statistical
language R was used to test the association between different genotypes
and body weights from birth up to eighteen months of age in both breeds.
In general, only three of nine SNPs showed a significant effect for
some body weights in both breeds. No PCR amplicon obtained for SNP3
and SNP7 in either breed, which may be due to improper primers design.
SNP1, SNP2, SNP8 and SNP9 showed only two genotypes that non significant effect for all body weights in both breeds. SNP4, SNP6 and
SNP10 showed significant association with some body weights in both
breeds. SNP4 showed significant association with body weights from 1wt
to 11wt and from 5wt to 18wt in Barki and Rahmani lambs, respectively.
SNP6 was significantly associated with body weights from 12wt to 14wt
and from 13wt to 18wt in Barki and Rahmani lambs, respectively. SNP10
was significantly associated with body weights from 10wt to 15wt and
from 4wt to 9wt in Barki and Rahmani lambs, respectively. The three
significant SNPs were found to be located on or close to three genes that
may be associated with body weights and growth performance. SNP4 was
downstream DPYSL5 gene, SNP6 was located within CYFIP2 gene and
SNP10 was located within SCARB1 gene. The reference/alternative allele
of SNP4 (C/T) was located on chromosome 3 bp 33779747 of Ovis aries
genome. The reference/ alternative allele of SNP6 (G/A) was located on
chromosome 5 bp 66.280.350 of Ovis aries genome with Id rs428550743.
The reference/alternative allele of SNP10 (G/A) was located on
chromosome 17 bp 50575955 of Ovis aries genome with Id rs404767873.
Annotation results for CYFIP2 and SCARB1 genes emphasize that
both genes are related directly or indirectly to growth performance. The
mechanism by which the polymorphism in both genes affects growth
performance has not been established. Whereas the polymorphisms
evaluated in the study do not result in amino acid substitutions, these
polymorphisms may be associated with other mutation(s) in other site(s)
of the nucleotide sequence or other genes closely linked with these genes.
It’s the first time to discover novel genes which may be associated with
growth performance in Egyptian sheep breeds using Allele-Specific PCR
technique. This SNPs can be used as genetic markers but it need further
emphasis. In conclusion, three SNPs (OAR3_ 33779747.1,
OAR5_66280350.1 and OAR17_50575955.1) and two genes (CYFIP2
and SCARB1) were detected in the study may be related to growth
performance in Barki and Rahmani breeds. The result of this chapter suggested that:
Three SNPs (OAR3_ 33779747.1, OAR5_66280350.1 and
OAR17_5057595 5.1) are recommended to use as genetic
markers for selecting Egyptian Barki and Rahmani lambs for
mutton production.
Two genes (CYFIP2 and SCARB1) were detected in the study
may be related to growth performance in Barki and Rahmani
breeds, are recommended to work on it in the near future.