Homology of single copy and repeated sequences in chicken, duck, Japanese quail, and ostrich DNA.

The extent of reassociation of 3H-labeled repetitive or single copy DNA sequences from the chicken with excess unlabeled DNA from the duck, the Japanese quail, and the ostrich, respectively, was measured by hydroxylapatite chromatography. Chicken repetitive DNA reassociated to an equal or greater extent than chicken single copy DNA with the DNA of each of the other birds. Using an isolated subfraction of chicken repetitive DNA representing those DNA sequences common to the chicken and ostrich genomes, we determined that many repetitive DNA sequences that occur at high repetition frequency in the chicken genome have a much lower repetition frequency in ostrich DNA. The data indicate that there has been a striking change in the number of copies of many repetitive DNA sequences during avian evolution.