-The field of Genome annotation pay a lot of attentions where the ability to collect and analysis genomical data can provide strong indicator for the study of life\cite{Eisen2007}. A lot of genome annotation centres present various types of annotations tools (i.e cost-effective sequencing methods\cite{Bakke2009}) on different annotation levels. Two method of gene finding in annotated genome can be categorized as: Alignment-based, composition based, or combination of both\cite{parra2007cegma}. The Alignment-based method is used when we try to predict a coding gene (i.e. Genes that produce proteins) by aligning DNA sequence of gene to the protein of cDNA sequence of homolog\cite{parra2007cegma}. This approache also used in GeneWise\cite{birney2004genewise} with known splicing signals. Composition-based mothod (known as \textit{ab initio} is based on a probabilistic model of gene structure to find genes and/or new genes accoding to the probability gene value, this method like GeneID\cite{parra2000geneid}. In this section, we will consider a new method of finding core genes from large amount of chloroplast genomes, as a solution of the previous method where stated in section two. This method is based on extracting gene features. The question now is how can we have good annotation genome? To answer this question, we need to focusing on studying the annotation accuracy\cite{Bakke2009}) of the genome. A general overview of the system is illustrated in Figure \ref{Fig1}.\\
+The field of genome annotation pays a lot of attentions where the
+ability to collect and analysis genomical data can provide strong
+indicators for the study of life\cite{Eisen2007}. Four of genome
+annotation centers (such as, \textit{NCBI\cite{Sayers01012011},
+Dogma \cite{RDogma}, cpBase \cite{de2002comparative},
+CpGAVAS \cite{liu2012cpgavas}, and CEGMA\cite{parra2007cegma}})
+present various types of annotation tools (\emph{i.e.} cost-effective
+sequencing methods\cite{Bakke2009}) on different annotation
+levels. Generally, previous studies used one of three methods for gene
+finding in annotated genome using these
+centers: \textit{alignment-based, composition based, or combination of
+both\cite{parra2007cegma}}. The alignment-based method is used when we
+try to predict a coding gene (\emph{i.e.}. genes that produce
+proteins) by aligning DNA sequence of gene to the protein of cDNA
+sequence of homology\cite{parra2007cegma}. This approach also is used
+in GeneWise\cite{birney2004genewise}. Composition-based method (known
+as \textit{ab initio}) is based on a probabilistic model of gene
+structure to find genes according to the gene value probability
+(GeneID\cite{parra2000geneid}). In this section, we consider a new
+method of finding core genes from large amount of chloroplast genomes,
+as a solution of the problem resulting from the method stated in
+section two. This method is based on extracting gene features. A
+general overview of the system is illustrated in Figure \ref{Fig1}.\\