Alternative Splicing, Amino Acid Sequence, Animals, Base Sequence, Biological Evolution, Cloning, Molecular, Conserved Sequence, DNA Primers, ELAV Proteins, ELAV-Like Protein 2, Embryo, Mammalian, Embryonic and Fetal Development, Exons, Gestational Age, Molecular Sequence Data, Nerve Tissue Proteins, Polymerase Chain Reaction, RNA, Messenger, RNA-Binding Proteins, Rats, Sequence Homology, Amino Acid