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J N Timmis

Publications and source records attributed to J N Timmis.

22 records · Page 2Linked to original sources
PubMed1975

The status of ribosomal RNA genes during nuclear DNA reversion in flax.

Heritable changes in plant weight and nuclear DNA content may be induced in certain varieties of flax by different fertilizer environments. The large stable form (L) has 16% more nuclear DNA that the small stable form (S). In subsequent generations in particular environments the nuclear DNA difference disappears, although the plant weight differences remain, while in other environments both DNA and plant weight differences are maintained. The large stable form has 56-70% more rRNA genes than the small stable form. The majority of this difference in rDNA is maintained in types where the nuclear difference has reverted. It is suggested that the expression of the flax genome may be susceptible to a reduction in the multiplicity of rRNA genes which limits the availability of protein synthetic machinery needed for growth.

Cell Nucleus↗
PubMed1975

The Relationship between Satellite Deoxyribonucleic Acid, Ribosomal Ribonucleic Acid Gene Redundancy, and Genome Size in Plants.

The buoyant density of ribosomal DNA is similar in species with or without satellite DNA, and in all species examined was distinguishable from that of the satellite DNA. In melon tissues (Cucumus melo) the percentage satellite DNA is not correlated with the percentage hybridization to ribosomal RNA. Satellite DNA sequences do not appear to be dispersed between those coding for ribosomal RNA. There is no correlation between the presence of satellite DNA and high ribosomal RNA gene redundancy, but there is a correlation between satellite DNA and small genome size, which results in a correlation between satellite DNA and a high percentage hybridization to ribosomal RNA. Satellite DNAs are defined as minor components after CsCI centrifugation.

Journal Article↗