A Long-Range and Two Short-Range Periodicities Are Superimposed in the 1.706-g/cm3 Satellite DNA from Calf Thymus

Abstract

The organization of repetitive sequences has been studied by restriction nuclease analysis of satellite DNAs from calf thymus. Several novel structural features have been found in the 1.706-g/cm3 satellite DNA (satellite 111). A long-range periodicity of 2350 base pairs detected by cleavage with restriction endonucleases Bsp or EcoRII and two short-range periodicities of approximately 22 and 11 base pairs found by digestion with restriction endonucleases Alu and Sau, respectively, are superimposed in the nucleotide sequence of this satellite DNA. About 14 % of the DNA present in long-range repeats lack the short-range periodicities. The length of the long-range repeats varies by multiples of approximately 22 base pairs. The distribution of the restriction sites in the satellite DNA is non-random. The evolution of this satellite DNA is not adequately explained by saltatory amplification and random divergence alone; unequal crossing-over and additional non-random processes are discussed.In the 1.723-g/cm3 satellite DNA (satellite 11) a periodicity of 45 base pairs has been found by cleavage with restriction endonuclease A h . The cleavage pattern of this satellite DNA is compatible with a 3 % random divergence of an originally homogeneous nucleotide sequence.

The primary structure of bovine satellite 1.715

“…3 has revealed that, in contrast with the other bovine satellite 1.706, 1.711a and 1.720b (11)(12)(13)(14), the 1.715 satellite is not organized in short tandem repeats. Its sequence is made up, however, of a very large number of repetitive elements, 92% of it being formed by repeats as long as, or longer than, 6 nucleotides (Table II).…”

“…3, which are a tandem duplication of a 21 nucleotide sequence. It is of interest that the sequence AGATGA, which is present 5 times in the 1.715 satellite is also found in the prototype sequence of the 1.720b satellite (13) and that the related sequence GAGATGA of the 1.715 satellite is present in the prototype sequence of the 1.706 satellite (13), because this establishes a homology link between the 1.706, 1.711a and 1.720b satellites, which are highly homologous with each other (11)(12)(13)(14), on one hand, and the 1.715 satellite and its 1.711b relative, on the other. The homology link indicates, in turn, a common evolutionary origin for all the satellites just mentioned.…”

“…These showed that the 1.706 satellite, which is organized in an unusual structure of superimposed long-and short-range repeats (11), consists of different variants of a basic 23 nucleotide sequence, which is itself composed of a dodecanucleotide and a related undecanucleotide (12). The basic prototype repeat of the 1.706 satellite exhibits a very high homology to the 46 nucleotide repeat of the 1.720b satellite, which is in turn composed of two related 23 nucleotide sequences (13).…”

Inserted Sequences in Bovine Satellite DNA's

“…It has a repeat unit of 1413 base pairs (bp), which have been sequenced. Two segments of the repeat unit exhibit high homology to the 1.706 satellite DNA previously analyzed (5). A third segment (termed INS) is completely unrelated to the 1.706 satellite, and it is likely that this segment is the result of an insertion into a 1.706-like satellite DNA (Fig.…”

Physical Analysis of a (dG+dC)-Rich Fraction of DNA Obtained From the Ovine Genome

“…In the studies reported below, we have chosen to use the organomercuric compound 3,6-bis(acetatomercurimethyl)-dioxane (BAM D) (Btinemann and Dattagupta 1973; see also Cortadas et al 1977). It is reported to show an affinity for (dA + n-rich regions of DNA, resulting in an increased buoyant density, and to exhibit a degree of sequence selectivity (Cortadas et al 1977;Macaya et al 1978;Streeck and Zachau 1978).…”