Molecular hybridization of iodinated 4S, 5S, and 18S + 28S RNA to salamander chromosomes.

Abstract

4S, 5S, and 18S + 28S RNA from the newt Taricha granulosa granulosa were iodinated in vitro with carrier-free 125I and hybridized to the denatured chromosomes of Taricha granulosa and Batrachoseps wrighti. Iodinated 18S + 28S RNA hybridizes to the telomeric region on the shorter arm of chromosome 2 and close to the centromere on the shorter arm of chromosome 9 from T. granulosa. On this same salamander the label produced by the 5S RNA is located close to or on the centromere of chromosome 7 and the iodinated 4S RNA labels the distal end of the longer arm of chromosome 5. On the chromosomes of B. wrighti, 18S + 28S RNA hybridizes close to the centromeric region on the longer arm of the largest chromosome. Two centromeric sites are hybridized by the iodinated 5S RNA. After hybridization with iodinated 4S RNA, label is found near the end of the shorter arm of chromosome 3. It is concluded that both ribosomal and transfer RNA genes are clustered in the genome of these two salamanders.

Spatial organization of transcription by RNA polymerase III

“…Other examples of tRNA gene clusters are mostly isolated cases within genomes that have predominantly scattered tRNA genes. Examples include salmon ( 70 ), brown trout ( 70 ), salamander ( 71 ), rat ( 72 ), mouse ( 73 ) and human ( 74 ).…”

Localization of 5S gene loci on polytene chromosomes of Glyptotendipes barbipes (Staeger) and transcription of RNA from these sites.

“…For example, Rhynchosciara angelae (Szabo et al . 1972), Zea mays (Wimber et al 1974) and Taricha granulosa (Leon 1976) have only single loci for transcription of 5S RNA. Exchange of DNA between non-homologous chromo somes is a possible mechanism by which repeated genes may be spread to different regions of the genome.…”