In this paper, we review the literature on the growing body of data demonstrating the rapid evolution of sex and reproduction related (SRR) genes and show how a paradigm shift to the study of SRR genes can provide new approaches to solving some of the old problems in evolutionary biology. The argument is based on (1) the growing scope and importance of sexual selection in evolution, (2) the growing number of case studies showing rapid evolution of sexual traits in a wide variety of taxa, (3) the faster rate of DNA sequence divergence in genes affecting sexual function and fertility, (4) the evidence for the involvement of novel traits/genes in sexual functions, and (5) a proposed sex/non-sex dichotomy of the gene pool affecting viability versus fertility. It is argued that the adoption of the sex/non-sex dichotomy of genes / traits can provide new perspectives on such problems as species concepts, modes (allopatric/sympatric) of speciation, Haldane's rule, reinforcement, and the founder effect. It is proposed that the evolutionary study of genes affecting viability versus fertility is the key to understanding the genetic basis of speciation.

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Barley (Hordeum vulgare L.) is potentially a new source of genes for wheat (Triticum aestivum L.) improvement. Wheat-barley chromosome recombinant lines provide a means for introgressing barley genes to wheat genome by chromosome engineering, and since these are expected to occur only rarely in special cytogenetic stocks, an efficient selection skill is necessary to identify them. To convert RFLP markers to barley allele-specific PCR markers useful for effective production of wheat-barley recombinant lines, 91 primer sets derived from RFLP clones which were previously mapped to the barley chromosomes were examined for PCR amplification using `Chinese Spring' wheat, `Betzes' barley and the wheat-barley chromosome addition lines. The polymorphisms were detected by an agarose gel electrophoresis of the PCR products without digestion with restriction enzymes. Out of 81 primer sets producing polymorphisms between the wheat and barley genomes, 26 amplified barley chromosome-specific DNAs which were confirmed to be located on the same chromosome as the RFLP markers by using the wheat-barley chromosome addition lines. These amplified DNAs represent barley allele-specific amplicons, which distinguish barley alleles from their wheat homoeologous counterparts. The present investigation revealed a higher probability for obtaining allele-specific amplicons from genomic DNA-derived RFLP markers than from cDNA-derived ones. The barley allele-specific amplicons developed in this study, namely, four for chromosome 2H, two for 3H, seven for 4H, eight for 5H, one for 6H and four for 7H, are suitable for identifying `Chinese Spring' wheat- `Betzes' barley recombinant chromosomes. However, one out of eight barley allele-specific amplicons on chromosome 5H did not detect a unique barley band in a `New Golden' barley chromosome 5H addition line of `Shinchunaga' wheat, indicating there may be a need to reconstruct allele-specific amplicons with different barley cultivars.

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We determined 5 sequences of Japanese macaque ABO blood group gene exon 7 (ca. 0.5kb) and 2 sequences for exon 5 and intron 6 (ca. 1.7kb). We compared those data with published sequences of other Old World monkey species, and the results suggest that alleles A and B were polymorphic in the ancestral species of macaques, and that B type allele evolved independently in macaque and baboon lineages.

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Previously, the allelic expansion of a 33-bp AT-rich minisatellite repeat has been reported to cause FRA16B, a distamycin A-inducible fragile site. Here, we identified a novel 35-bp minisatellite repeat at FRA16B in a Japanese carrier. The nucleotide sequence of the 35-bp minisatellite was highly AT-rich and nearly identical to the 33-bp one but with insertion of two nucleotides, thymine and adenine. The copy number of the AT-rich minisatellite was 21 in total in the carrier, while only a few copies of the 33-bp minisatellite were present in a non-carrier Japanese subject. These results suggest that the molecular mechanism involved in the allelic expansion of the minisatellite repeat in FRA16B recognizes both minisatellites, the 33-bp one and the 35-bp one, as an amplicon. These observations were different from the ones at folate-sensitive fragile sites, where the CCG triplet repeat was commonly involved in the allelic expansion. Although a slight reduction in AT content (95%>90%) in the region of minisatellite expansion in the carrier subject was observed, both AT-content and length of the highly AT-rich region seem to play important roles in the cytogenetic expression of the distamycin A-inducible fragile site. In another normal subject, without fragile site expression, allelic expansion involving the 33-bp minisatellite was observed, and the length of the AT-rich DNA region was increased up to ~1000 bp. Since the length of the AT-rich minisatellite region was increased up to ~1,100-bp in the carrier subject, the threshold length for the cytogenetic expression of the AT-rich DNA region may be between about 1,000-bp and 1,100-bp.

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The house musk shrew, Suncus murinus, is polymorphic for five Robertsonian translocations (Rb8.17, 9.13, 10.12, 11.16, 14.15). Fluorescence in situ hybridisation with a biotin-labelled oligonucleotide, (TTAGGG)₇, was performed to localise the telomeric DNA sequences at Rb chromosomes of heterozygous shrews. Hybridisation signals were observed at both ends of all chromosomes, but not at the pericentromeric areas of any of the Robertsonian metacentrics. Our results indicate a complete loss of the telomeric sequences at the fusion points of the Rb metacentrics in S. murinus.

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A linkage map was constructed for the sawfly, Athalia rosae (Hymenoptera), based on the segregation of random amplified polymorphic DNA (RAPD) markers and a visible mutation, yellow fat body (yfb). Forty haploid male progeny (20 yfb and 20 +) from a single diploid female parent (yfb/+) were examined. Sixty-one of the 180 arbitrary primers tested by polymerase chain reaction (PCR) produced one or more RAPD bands. A total of 79 RAPD markers were detected. Of these, seven showed significant deviation from the expected 1:1 ratio, and were therefore excluded from further analysis. The remaining 72 RAPD markers and the marker mutation, yfb, were subjected to linkage analysis. Sixty RAPD markers and the yfb marker were organized into 16 linkage groups, spanning a distance of 517.2 cM. Twelve RAPD markers showed no linkage relationship to any group. Thirteen gel-purified RAPD bands were cloned and sequenced to generate the sequence-tagged sites (STSs). A single locus was represented by two markers, with one of them having a short internal deletion.

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Wild and cultivated hexaploid oats share the same genomes (AACCDD) and display a considerable level of interspecific variation in both plant and chromosome morphology. The GISH was utilized to detect the interspecific genomic compositions in four hexaploid and two tetraploid oats using total genomic DNA of Avena eriantha (a C-genome diploid) as probe. Intergenomic translocations between A/D and C-genome chromosomes were frequently observed in hexaploid and tetraploid species. In the hexaploid, two pairs of A/D genome segments on C-genome chromosome (A/D-C) translocation and four to six pairs of C-genome segments on A/D genome chromosome (C-A/D) translocation were clearly identified whilst the number of A/D-C translocations was constant among species. In the tetraploid A. maroccana (AACC), a pair of A-C and four pairs of C-A translocations were observed. Moreover, the A/D translocation segments on chromosome 5C was detected only in A. byzantina and A. maroccana, whilst A/D-C translocations were observed on the 1C and 7C of A. sativa, A. fatua and A. sterilis. A. byzantina did however also carry the 1C rearrangement. This result shows that A. byzantina has retained a similar genomic constitution to the tetraploid ancestor of hexaploid oats, A. maroccana. Three pairs of A-C translocations were detected only in A. murphyi (AACC), and two pairs of those were the 1C and 7C as well as the three hexaploid species except A. byzantina.

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