**3. Brief characteristics of Marek's disease virus genes**

MDV genes can be divided into three groups:


The best described and characterized gene is the meq gene. It is a protein that is present only in serotype 1 strains. It plays an important role in oncogenesis and its sequence has been used to develop primers for an amplification reaction in which a single reaction can distinguish field strains from the Rispens CVI 988 vaccine strain [29].

Another important oncogenic gene is the pp38 gene. It occurs in both strains belonged to serotype 1 and serotype 3, where it shows a high homology [30].
