Changes in DNA composition during cell differentiation in a green alga.

In the coenobia-forming green alga, Hydrodictyon reticulatum, changes in DNA composition during growth and differentiation of reproductive cells were followed. A "loss" of DNA per nucleus could be attributed to underreplication of an amplified DNA fraction being part of a (GC)-rich satellite band in CsCl gradients of DNA from young coenobia. This (GC)-rich satellite DNA contains up to 3 % unique DNA sequences intermingled with repetitive DNA. It does not (or nearly not) contain ribosomal DNA. A possible role of this DNA fraction in differentiation is suggested.