Topic
Nuclear DNA
About: Nuclear DNA is a research topic. Over the lifetime, 3933 publications have been published within this topic receiving 185830 citations.
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TL;DR: The 4C DNA amounts of 86 species from Allium subgg.Allium, Rhizirideum, Bromatorrhiza, Melanocrommyum, Caloscordum andAmerallium show a 8.35-fold difference, which shows that a significant loss and/or gain of DNA has occurred during evolution.
Abstract: The 4C DNA amounts of 86 species fromAllium subgg.Allium, Rhizirideum, Bromatorrhiza, Melanocrommyum, Caloscordum andAmerallium show a 8.35-fold difference ranging from 35.60 pg (A. ledebourianum, 2n = 16) to 297.13 pg (A. validum 2n = 56). At diploid level the difference is 3.57-fold betweenA. ledebourianum (35.60 pg) andA. ursinum (127.14 pg). This shows that a significant loss and/or gain of DNA has occurred during evolution. On average subgg.Rhizirideum andAllium have less DNA amount than subgg.Melanocrommyum andAmerallium. The distribution of nuclear DNA amounts does not show discontinuous pattern and regular groups. The evolution of genome size has been discussed in relation to polyploidy and genomes, heterochromatin, adaptive changes in morphological characteristics, phenology and ecological factors, and infrageneric classification.
78 citations
TL;DR: To cover a wide range of possible demographic situations in the human lineage since the Miocene, a model is introduced that allows temporal changes in population structure and size and the coalescence process of neutral genes is formulated and used to make quantitative inferences on the origin and history of humans.
Abstract: Recent topics in molecular anthropology are reviewed with special reference to hominoid DNA sequences and population genetics theory. To cover a wide range of possible demographic situations in the human lineage since the Miocene, a model is introduced that allows temporal changes in population structure and size. The coalescence process of neutral genes is formulated and used to make quantitative inferences on the origin and history of humans. Nuclear DNA sequence data support the theory that humans and chimpanzees diverged from each other 4.6 million years (mya) and the gorilla lineage branched off as early as 7.0-7.4 mya. The same data estimate the effective size of the Pliocene hominoid population as i05, a figure similar to that obtained independently from alleles that have persisted in the human population for more than 5 my. Hypotheses about the origin of Homo sapiens, genetic differentiation among human populations, and changes in population size are quantified. None of the hypotheses seems compatible with the observed DNA variation. The effective population size decreased to 104 in the Pleistocene, suggesting an important role of extinction/restoration in H. sapiens populations. Natural selection against protein variation might be relaxed in the Pleistocene. The 'Abbreviation and symbols: kb (kilo base pairs), bp (base pairs), yr (years), my (a) (million years (ago)), COII (cytochrome oxidase subunit II), rDNA (ribosomal DNA), mtDNA (mitochondrial DNA), MHC (major histocompatibility complex)
78 citations
TL;DR: It is concluded that egg cytoplasm contains an enzyme system capable of replicating native DNA of vertebrate but not of bacterial origin, and that the components of egg or sperm nuclei other than their DNA are not essential for the initiation of the nuclear DNA synthesis that normally follows fertilization.
78 citations
TL;DR: The environment has been shown to induce heritable changes in three plant systems, namely flax, Nicotiana rustica, and soybean cell suspension cultures, and the phenomenon of environmentally induced DNA variation is compared with examples of gene amplification or deletion in other systems.
Abstract: The environment has been shown to induce heritable changes in three plant systems, namely flax, Nicotiana rustica, and soybean cell suspension cultures. Changes in nuclear DNA sequences associated with the induction phenomenon have been demonstrated in both flax and soybean. In flax, which has been most extensively studied, the overall variation in the nuclear DNA is described together with a number of transcribed and nontranscribed sequences which have been shown to vary. Possible mechanisms by which the observed DNA changes could arise are discussed and the phenomenon of environmentally induced DNA variation compared with examples of gene amplification or deletion in other systems.
78 citations
TL;DR: The maintenance of the spotted appearance of the replication clusters through all stages of the three subsequent cell cycles may be an indication in favour of the hypothesis that such clusters represent structurally stable replicon complexes held together by the nuclear matrix and the chromosome scaffold.
Abstract: Nuclear DNA replication was monitored 'in situ' in pea nuclei with the bromodeoxyuridine antibody technique. The labelling appeared to be restricted to a number of finely distinct spots. The labelling was followed through three subsequent cell cycles in meristematic and differentiating pea root cells. The results show that the spots as seen just after the labelling persist distinctly over the mitotic chromosomes as well as in the nuclei of the following cell cycles up to 44 hours after the pulse. Moreover, they are also present in the nuclei of differentiating cells. The spots over the mitotic chromosomes in specific cases give rise to a dynamic banding. Nuclei of the second and third cycle show absence of labelling in specific zones, owing to the segregation of the labelled strands of chromosomal DNA. The maintenance of the spotted appearance of the replication clusters through all stages of the three subsequent cell cycles may be an indication in favour of the hypothesis that such clusters represent structurally stable replicon complexes held together by the nuclear matrix and the chromosome scaffold.
78 citations