SINGLE-STRANDED NUCLEIC-ACID BINDING STRUCTURES ON CHICKEN LAMPBRUSH CHROMOSOMES

In chicken oocytes, proteins of the K/J family or their analogs, such as are known to be involved in mRNA processing in humans, are closely associated with nascent C-rich RNA transcripts on the loops of lampbru sh chromosomes, Using labelled single stranded nucleotide probes and a n antibody to protein K, these C-rich transcripts have been mapped to six different pairs of lampbrush loops situated on 3 macrochromosomes, the sex bivalent (ZW) and certain microchromosomes. Each of these loo p pairs has a distinctive morphology, The observations represent cytol ogical evidence of the connection between K-proteins and C-rich RNA tr anscripts, Another structure, the spaghetti marker of macrochromosome II, also preferentially binds C-rich homonucleotides. This spaghetti m arker has a highly distinctive fine structural organization that is qu ite unlike that of lampbrush loops, Its proteins are not recognised by antibodies to protein K. Homonucleotide binding loops are recommended as potentially extremely valuable as markers on physical maps of chic ken chromosomes.