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J D Rochaix

Publications and source records attributed to J D Rochaix.

At least 109 records · Page 6Linked to original sources
PubMed1981

Nucleotide sequence and structure of cytoplasmic 5S RNA and 5.8S RNA of Chlamydomonas reinhardii.

Three small RNAs of the cytoplasmic 8OS ribosomes of the green unicellular alga Chlamydomonas reinhardii have been sequenced. They include two species of ribosomal 5S RNA, a major and a minor one of 122 and 121 nucleotides respectively, which differ from each other by 17 bases, and also the ribosomal 5.8S RNA of 156 nucleotides. Novel structural features can be recognized in the 5S RNAs of C. reinhardii by a comparison with published 5S RNA sequences. In addition the secondary structure of these small RNA molecules has been examined using a newly developed method based on differential nuclease susceptibility.

Base Sequence↗
PubMed1981

Comparison of the nuclear ribosomal units of five Chlamydomonas species.

The organization of the nuclear ribosomal units of five different species of Chlamydomonas has been examined by hybridization of their nuclear DNA fragments produced by several restriction endonucleases with a radioactively labelled probe consisting of the two cloned BamHI ribosomal fragments of C. reinhardii. The results indicate that a) the ribosomal units of these five species are structurally related, b) changes in the non transcribed spacer occur in C. eugametos and in C. globosa, c) the rDNA unit of C. intermedia contains either an enlarged internal transcribed spacer or a ribosomal intervening sequence, d) the rDNA units of C. reinhardii and C. callosa are indistinguishable.

Chlamydomonas↗
PubMed1980

Organization of the nuclear ribosomal DNA of Chlamydomonas reinhardii.

Hybridization of cytoplasmic ribosomal RNA (rRNA) to restriction endonuclease digests of nuclear DNA of Chlamydomonas reinhardii reveals two BamHI ribosomal fragments of 2.95 and 2.35 x 10(6) d and two SalI ribosomal fragments of 3.8 and 1.5 x 10(6) d. The ribosomal DNA (rDNA) units 5.3 x 10(6) d in size, appear to be homogeneous since no hybridization of rDNA to other nuclear DNA fragments can be detected. The two BamHI and SalI ribosomal fragments have been cloned and a restriction map of the ribosomal unit has been established. The location of the 25S, 18S and 5.8S rRNA genes has been determined by hybridizing the rRNAs to digests of the ribosomal fragments and by observing RNA/DNA duplexes in the electron microscope. The data also indicate that the rDNA units are arranged in tandem arrays. The 5S rRNA genes are not closely located to the 25S and 18S rRNA genes since they are not contained within the nuclear rDNA unit. In addition no sequence homology is detectable between the nuclear and chloroplast rDNA units of C. reinhardii.

Chlamydomonas↗
PubMed1979

Structure analysis at the ends of the intervening DNA sequences in the chloroplast 23S ribosomal genes of C. reinhardii.

All of the chloroplast 23S ribosomal genes of C. reinhardii are interrupted by a 0.87 kb sequence (Rochaix and Malnoë, 1978). We have sequenced the DNA across the two ends of this intervening element. In parallel, we have examined the nucleotide sequences in the corresponding part of the 23S ribosomal RNA. This allowed us to locate precisely the boundaries between the coding (that is, transcribed into mature 23S rRNA) and the noncoding DNA. The results show that the intervening sequence is flanked by two identical sets of 3 bp (5'-CGT) oriented as direct repeats. In addition, a sequence of 5 bp (5'-CGTGA) lies exactly next to one end and is found very close (16 bp) to the other end, in the coding part of the gene. These two sets are also oriented as direct repeats. Finally, sequences near one end of the intervening element are found with a few alterations near the other end, but in an inverted orientation. Possible interpretations of these results are discussed.

Base Sequence↗
PubMed1978

Localization of 4S RNA genes on the chloroplast genome of Chlamydomonas reinhardii.

The genes coding for 4S RNA have been localized on the physical map of the chloroplast genome of Chlamydomonas reinhardii by hybridizing 32P-labelled 4S RNA to EcoRI, BamHI, Bg1II and Hind III chloroplast DNA digests and to hybrid plasmids containing EcoRI and Bam HI chloroplast DNA fragments. At least 10 EcoRI and 7 Bam HI fragments carry sequences coding for 4S RNA. These genes are interspersed throughout the genome. The spacer between the 16S and 23S ribosomal RNA genes, which is repeated twice per chloroplast DNA molecule, codes for at least one 4S RNA, shown to be transcribed from the same strand as the ribosomal RNAs.

Chlamydomonas↗
PubMed1978

Electron microscope analysis of mouse and rabbit globin and immunoglobulin gene sequences.

Mouse and rabbit globin and immunoglobulin gene sequences, which had been synthesized in vitro from eukaryotic mRNAs and inserted into plasmids, have been examined in the electron microscope. The size of the inserted beta rabbit and alpha and beta mouse globin DNA sequences has been estimated as 620 base pairs while the size of the inserted alpha rabbit globin DNA sequences was found to be about 490 base pairs. Heteroduplex analysis has revealed no structural abnormalities at the insertion sites of the chimeric plasmids except in the case of a plasmid containing an immunoglobulin light chain gene sequence of about 830 bases, in which 3 kb deletion adjacent to the insertion site was observed.

Animals↗
PubMed1975

Circular ribosomal DNA and ribosomal DNA: replication in somatic amphibian cells.

Pulse labelled rDNA from cultured somatic cells of Xenopus laevis was examined by electron microscope autoradiography. The pattern of replication closely resembles that of bulk chromosomal DNA and differs considerably from rDNA synthesis during amplification in the oocyte. - About 0.15% of the rDNA molecules in the purified preparations were circular. The presence of interlocked circles of equal size indicates that the circles are not in vitro cyclization artefacts, but may represent free rRNA genes. A low frequency of circles was also seen in Xenopus blood rDNA. Their stability in high concentration of formamide suggests that they too did not arise after DNA extraction.

Animals↗
PubMed1975

Transposition of R factor genes to bacteriophage lambda.

Transpositions of segments of R factor (antibiotic resistance plasmids) to bacteriophage lambda have been selected and characterized. Cells of Escherichia coli harboring R factors that determine kanamycin resistance were infected with phage lambda, and lambdakan transducing lines were obtained. Each of the three examined is unusual when compared to lambda transducing phages containing E. coli chromosomal genes: the kan insertions (a) occur at several sites, each well removed from the integration region POP', (b) are not associated with deletion of lambda phage DNA, and (c) are separable from the lambda genome during transduction or during lytic growth. Two insertions from the same R factor contain 1.5 kilobase sequences repeated in inverted order. The properties of the lambdakan phage suggest that R factors contain systems capable of mediating genetic exchange in the absence of extensive DNA homology. It is suggested that such systems of exchange may have played important roles in R factor evolution.

Chromosome Mapping↗
PubMed1974

The amplified ribosomal DNA of dytiscid beetles.

During oogenesis in many animals there is a massive extrachromosomal synthesis of the genes for ribosomal RNA. In Dytiscid beetles, as in the toad Xenopus, the amplified ribosomal DNA occurs as circular molecules of different sizes. The circles fall into size classes that are integral multiples of a unit circle. It is probable that the unit circle contains the coding sequence for one precursor ribosomal RNA molecule plus accompanying spacer sequences.

Animals↗
PubMedDate not supplied

Studies on homologous recombination in the green alga Chlamydomonas reinhardtii.

The introduction of exogenous DNA into the nuclear genome of Chlamydomonas reinhardtii occurs predominantly via non-homologous (illegitimate) recombination and results in integration at apparently-random loci. Using truncated and modified versions of the C. reinhardtii ARG7 gene in a series of transformation experiments, we demonstrate that homologous recombination between introduced DNA molecules occurs readily in C. reinhardtii, requires a region of homology of no more than 230 bp, and gives rise to intact copies of ARG7 in the nuclear genome. Evidence is presented for homologous recombination between introduced ARG7 DNA and the resident copy of the gene, and for the de-novo synthesis of the ARG7 sequence during transformation.

Animals↗