Synthesis of a Deoxyribonucleic Acid Sequence Complementary to Ovalbumin Messenger Ribonucleic Acid

SUMMARY DNA was synthesized in vitro from a template of purified ovalbumin messenger RNA. The DNA product is complementary to a homogeneous sequence specific for ovalbumin. The amount of ovalbumin sequence in hen oviduct and hen liver DNA was measured by hybridization experiments and found to be 2 copies per diploid genome in both tissues, indicating that there is no selective amplification of ovalbumin genes in the tissue specialized for obalbumin synthesis. Both DNA (l-3) and RNA (4) polymerases can be used to synthesize nucleic acid sequences complementary to hemoglobin messenger RNA. Such sequences, specific for a given polypeptide, can be used in molecular hybridization experiments to estimate the quantity of information coding for that polypeptide in a given population of nucleic acid molecules (5-7). We have previously reported the purification of messenger RNA for chicken ovalbumin by selective immunoadsorption of ovalbumin polyribosomes and subsequent adsorption of messenger RNA to nitrocellulose filters (8). The present communication describes the preparation of DNA complementary to this messenger RNA using the RNA-directed DNA polymerase of Rous sarcoma virus (9). Analysis of this DNA by molecular hybridization experiments indicates that the enzymatic product represents a homogeneous set of nucleotide sequences specific for