RT-PCR analysis of hybrid PK-bcl-2 transcripts on hematopoietic colonies. Granulocytic and BFU-E–derived colonies were individually plucked from the methylcellulose under direct microscopic visualization 7 days after plating, total RNA of each sample was extracted, and used for RT-PCR amplification. The PK-bcl–2-specific amplified fragment is 260 bp long.