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This survey included 1250 tetrads from 19 families heterozygous for at least three genes on chromosome V. A number of tests were used for the detection of interference. The Papazian tests (table 1) indicated that either positive chromosomal interference or negative chromatid interference occurs in some regions; this effect is too weak to be manifest in individual families. Although chromosomal interference was not evident in the three-point tests of any one family, there was some evidence from lumped data that it occurs. Negative chromatid interference is clearly evident in the three-point tetrad data. This effect varies from family to family, and does not appear to be localized to certain regions. The data indicate that chromatid interference is a property conferred by the specific hybrid rather than a fixed property of any given chromosomal region. In this connection it is interesting to note that family 118, which exhibits chromatid interference, was obtained from a intraascal hybrid from family 108, which also shows chromatid interference, suggesting that this family-specific effect may be hereditary.

The genetic diversity in the wild and semi-domestic populations of Daba ecorace of Antheraea mylitta was studied to ascertain the distribution of variability within and among populations of semi-domestic bivoltine (DB), trivoltine (DT) and nature grown wild populations (DN) with inter-simple sequence repeat (ISSR) markers. A total of 138 markers were produced among 56 individuals of the three populations, of which 98% were polymorphic. For the individual populations, the percentage polymorphism was 58.69, 52.9 and 77.54 for DB, DT and DN, respectively. Average number of observed (1.791 ± 0.408) and effective alleles (1.389 ± 0.348) was also high in the wild populations in comparison to the bivoltine and trivoltine semi-domestic populations. Genetic diversity (Ht) in DB, DT and DN was 0.180 ± 0.033, 0.153 ± 0.032 and 0.235 ± 0.033, respectively and within-population genetic diversity (Hs) ranged from 0.166 to 0.259 with a mean of 0.189. Mean gene differentiation (GST) was found to be 0.25. Shanon’s diversity index was 0.278, 0.237 and 0.361 for DB, DT and DN and overall it was 0.391. Gene flow (Nm) among the populations was 1.509. The dendrogram produced by UPGMA with Dice’s genetic distance matrices resulted in the formation of three major clusters separating the three populations. Considerable intra- and inter-population variability is found in all three populations. The population structure analysis further suggests that the semi-domestic populations of Daba ecorace are at the threshold of differentiating themselves. The high genetic variability present within wild Daba population of A. mylitta is of much importance for conservation as well as utilization in systematic breeding program.

Of 35 species of Crotalaria (Leguminosae) studied, all but one had usually one nucleolus in the premetaphase I cells. In C. agatiflora 300 PMCs from four out of five plants were investigated and the percentage cells with more than one nucleolus was determined as well as the nature of nucleolar attachment to bivalents and the range and the sizes of various nucleoli present in the cell. The ‘aberrant’ cells ranged from 42 to 50%. The nucleoli (1–6) were usually attached to different bivalents. Where one nucleolus was present in the cell, it was always attached to an X-shaped bivalent, formed of a pair of nucleolar chromosomes. In the aberrant cells one nucleolus usually was attached to such a bivalent. The presence of accessory nucleoli has been attributed to hybridity as a result of large-scale intercrossing among five subspecies and consequent dispersal of intermediates in the adjoining areas where C. agatiflora grows wild (East Africa and Ethiopia). The change in the regulatory system of the cell caused by hybridity results in activation of latent nucleolar organizers, although their overall presence in the genome is not due to hybridity.

LTR-retrotransposons are ubiquitous and highly abundant in plant genomes. Moreover, LTR-retrotransposons can often cause genome obesity in plants. Although Lilium species have been known carrying large genomes among flowering plants, reports on the LTR-retrotransposons in Lilium species are rather limited. We isolated a novel Ty3/gypsy-like retrotransposon, LIRE-del, and two Ty1/copia-like retrotransposons, a LIRE-del and an unclassified, from a fosmid clone of Lilium longiflorum. Decayed internal ORF sequences indicated that they were non-autonomous elements. IRAP protocol was developed based on the LTR sequences of the isolated LTR-retrotransposons. Fourteen primer combinations showed clear distinctive PCR amplification bands that were highly informative in the analysis of species relationship among Lilium species. The phylogenetic relationship based on the IRAP profile revealed some discordant with phylogenetic studies based on the ITS sequences of 45S ribosomal gene and matK gene variations in a few species. Thus, the phylogenetic relationship among Lilium species may need to be re-evaluated with other tools such as cross compatibility and selectively neutral genetic markers.

A homoeotic strain in which wing-like outgrowths are produced from the eye region was investigated. The actual wing nature of the malformation was confirmed. Genetically, this homoeotic character depends on the presence of an eye-reducing factor,loboid (ld; 3–102), and of modifier genes. One important sex-linked modifier, probably located at 1–5±, is thought to be the main factor underlying the homoeotic effect. It is designated asopht (ophthalmoptera), and the mutant strain asld-opht Kobel (1968), assuming a specific allele ofld with homoeotic effect, originally described this strain under the nameld oph. It is shown that inld-opht, theld factor can be replaced byDfd r-L (3–47.5) without irrevokably losing the homoeotic effect. Penetrance and expressivity ofopht are very variable and subject to genetic and environmental changes, and they readily respond to selection. Such properties are common to all homoeotic mutants. The phenomenon of homoeosis is interpreted in terms of allotypic differentiations resulting from a switching of development into other epigenetic pathways. This switching is perhaps due to an altered rate of proliferation.

We describe here two new transposable elements, CemaT4 and CemaT5, that were identified within the sequenced genome of Caenorhabditis elegans using homology based searches. Five variants of CemaT4 were found, all non-autonomous and sharing 26 bp inverted terminal repeats (ITRs) and segments (152–367 bp) of sequence with similarity to the CemaT1 transposon of C. elegans. Sixteen copies of a short, 30 bp repetitive sequence, comprised entirely of an inverted repeat of the first 15 bp of CemaT4’s ITR, were also found, each flanked by TA dinucleotide duplications, which are hallmarks of target site duplications of mariner-Tc transposon transpositions. The CemaT5 transposable element had no similarity to maT elements, except for sharing identical ITR sequences with CemaT3. We provide evidence that CemaT5 and CemaT3 are capable of excising from the C. elegans genome, despite neither transposon being capable of encoding a functional transposase enzyme. Presumably, these two transposons are cross-mobilised by an autonomous transposon that recognises their shared ITRs. The excisions of these and other non-autonomous elements may provide opportunities for abortive gap repair to create internal deletions and/or insert novel sequence within these transposons. The influence of non-autonomous element mobility and structural diversity on genome variation is discussed.

In crosses betweenP. lagopus trisomic for chromosome 4 and normal disomics the extra chromosome is transmitted to about 1/4 of the progeny through the male side and to over 1/2 on the female side. Among the progeny some non-parental types which include a tetrasomic (2x + 2) and an aneutriploid (3x + 1) were also found. Chromosomal behaviour during their male meiosis is described.