Quantitative nuclear variation in inbred lines and hybrid rye

Abstract

SUMMARYQuantitative effects of inbreeding depression and heterosis in rye have been analysed at three levels of organisation: (i) the plant, (ii) the cell and (iii) the nucleus.(i) Hybrid plants have a higher mean fresh weight than the inbred lines over the first few weeks of growth. This is accounted for by a faster rate of growth and also by some initial advantages in seed weight. (ii) There is a difference in the cellular organisation of root meristems.Hybrids have almost twice as many cells per unit fresh weight as inbred lines. (iii) At the nuclear level, in root meristem nuclei, hybrids have greater amounts of total protein and RNA and smaller amounts of histone than do the inbred lines.

Homeostasis, enzymatic heterozygosity and inbreeding depression in natural populations of Drosophila melanogaster

“…This is particularly relevant since deletions and duplications of small DNA segments are postulated to be the most general processes by which most evolutionary changes in the genome have taken place (Bachmann, (Join & (Join, 1974). Searching for an association between inbreeding and the regulation of gene expression should be useful as illustrated by the finding of Kirk and Jones (1974), who showcd that nuclear histones increase in inbred lines, suggesting thus an increasing repression of genetic activity.…”

Are imprinting and inbreeding two related phenomena?

“…The inbreeding depression thus results in a low viability due to numerous causes of mortality throughout the development of the organism (Lewontin, 1974); viability has thus been postulated to be controlled by polygenes with an extremely high spontaneous mutation rate (Simmons and Crow, 1977 (Wright, 1921(Wright, , 1922aMal6cot, 1948;Haldane, 1954;Lerner, 1954;Dobzhansky et al, 1963) (Holliday, 1987), and that some specific interactions which survive to transmit the memory can themselves be heritable (Weintraub, 1985); it is also supported by the recent observation of the failure of the germline in mice to erase the epigenetic modifications at the TKZ751 locus, thus leading to cumulative modifications of this locus through successive generations (Allen et al, 1990 (Kirk and Jones, 1974) and a disappearance of some biochemical components in Drosophila (Hoenigsberg and Castiglioni, 1958;King, 1969) (Cole and Halpin, 1916;Dunn, 1928 (Johnson et al, 1981). It (Bi6mont, 1974b(Bi6mont, , 1980Biémont et al, 1974 (Falconer, 1981).…”