Journal of Applied Biosciences (J. Appl. Biosci.) [ISSN 1997 - 5902]
Volume 64: 4858 - 4866 Published April 25, 2013.
Genetic variations of β- and K-casein genes in Egyptian sheep breeds
Othman E. Othman1, Samia A. El-Fiky1, Nagwa A. Hassan2, Eman R. Mahfouz1 and Esraa A. Balabel11 Cell Biology Department, National Research Center, Dokki, Egypt
2 Zoology Department, Ain Shams University, Cairo, Egypt
* Corresponding author: Dr. Othman El Mahdy Othman, Cell Biology Department, National Research Center, Dokki - Giza – Egypt. Fax.: 202 33370931 E-mail: othmanmah@yahoo.com
Original submitted in on 1st March 2013. Published online at www.m.elewa.org on 25th April 2013.
ABSTRACT
Objective:
Casein genetic polymorphisms are important and well known due to their
effects on quantitative traits and technological properties of milk
manufacturing. The casein fraction of ruminant milk proteins consists
of four caseins, namely αs1-, αs2-, β-and K-casein. At the DNA level,
polymerase chain reaction (PCR) and single-strand conformation
polymorphism (SSCP) allow for the simultaneous typing of several
alleles at casein loci, as well as the detection of unknown
polymorphisms. The genetic polymorphism of two ovine milk protein
casein genes, β- and K-caseins, was studied in sheep animals belonging
to three main breeds reared in Egypt (Rahmani, Barki and Ossimi), as a
tool for genetic improvement of milk trait characteristics.
Methodology and results: SSCP of β-casein exon 7 revealed two different patterns in eighty-five tested animals. The sequence analysis of the PCR product (299-bp) of these two different patterns showed two single nucleotide substitutions; AC and CT without any amino acid exchange. The frequencies of these two different patterns were 96.67% and 3.33% in Rahmani; 65.52% and 34.48% in Ossimi and 88.46% and 11.54% in Barki, respectively. The nucleotide sequence of β-casein in Egyptian sheep was submitted in database NCBI/ GenBank with the accession number JX080380. The polymorphism of K-casein gene was also detected in eighty-six animals using PCR-SSCP technique. PCR amplified a fragment with 406-bp in exon 4 of this gene. SSCP results showed that all tested sheep animals are monomorphic. The alignment between our sequences with published sequence revealed two nucleotide substitutions; CT and TC. The nucleotide sequence of K-casein in our tested animals was submitted in database NCBI/ GenBank with the accession number JX050176.
Conclusion and application of findings: This study aimed to identify the genetic polymorphism of β and K-casein genes, which are strongly related to economically important milk quantitative traits in some Egyptian sheep breeds, as a tool or genetic markers for improvement of these breeds.
Key words: Sheep, β-casein, K-casein, PCR-SSCP, SNP.Methodology and results: SSCP of β-casein exon 7 revealed two different patterns in eighty-five tested animals. The sequence analysis of the PCR product (299-bp) of these two different patterns showed two single nucleotide substitutions; AC and CT without any amino acid exchange. The frequencies of these two different patterns were 96.67% and 3.33% in Rahmani; 65.52% and 34.48% in Ossimi and 88.46% and 11.54% in Barki, respectively. The nucleotide sequence of β-casein in Egyptian sheep was submitted in database NCBI/ GenBank with the accession number JX080380. The polymorphism of K-casein gene was also detected in eighty-six animals using PCR-SSCP technique. PCR amplified a fragment with 406-bp in exon 4 of this gene. SSCP results showed that all tested sheep animals are monomorphic. The alignment between our sequences with published sequence revealed two nucleotide substitutions; CT and TC. The nucleotide sequence of K-casein in our tested animals was submitted in database NCBI/ GenBank with the accession number JX050176.
Conclusion and application of findings: This study aimed to identify the genetic polymorphism of β and K-casein genes, which are strongly related to economically important milk quantitative traits in some Egyptian sheep breeds, as a tool or genetic markers for improvement of these breeds.
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