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A second isotype of Raja immunoglobulin heavy chain genes has been detected by screening a spleen cDNA library with homologous Raja VH - and CH1 - specific probes complementing the respective regions of the mu - like isotype .
 Raja immunoglobulin heavy chain genes, Raja VH, CH1, mu - like isotype
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 Raja immunoglobulin heavy chain genes, Raja VH, CH1, mu - like isotype