Genetic differentiations between randomly and selectively bred pig populations in Yunnan, China.

To assess the genetic diversity between randomly and selectively bred populations, we sequenced 438 bp of the mitochondrial DNA control region from 102 pigs. These samples represented four native pig breeds, one nucleus and one conservation herd from Yunnan, China. Twenty haplotypes with sixteen polymorphic sites were identified. The number of haplotypes in the nucleus herd of Saba pig and the conservation herd of Banna miniature pig were restricted to three and one, respectively, while the randomly bred pig populations exhibited over six haplotypes. Notably, haplotype diversity in randomly bred populations was significantly greater than the selectively bred populations (h=0.732 vs. 0.425 and 0, exact test, P<=0.0036). These findings demonstrate that selective breeding generated low genetic diversity compared to randomly bred pig breeds. A timely intervention and well programmed breeding approach would stop further genetic diversity reduction in the nucleus and conservation herds of native pig breeds. Otherwise, selective breeding would dramatically reduce genetic diversity in only several years, indicating that sharp contradictions exist between breeding, conservation and genetic diversity. Genetic relationships are discussed based on net genetic distances among pig populations.

[Identification of a common deletion in different curly mutants in Drosophila melanogaster].

Curly is a easily distinguishable dominant mutant wing character. The Cy mutation is the most commonly used dominant marker for the second chromosome balancers in Drosophila melanogaster, but little is known about the Cy gene. Based on known genomic and cytogenetic information, a 102 bp deletion which is located between the Genes synaptotagmin (syt) and Activin Like Protein at 23B(Alp23B) on the Drosophila melanogaster genome (release 4) had been found to be commonly contained on Cy chromosome in three different curly strains. Meanwhile, when using the deletion as a DNA marker, the result suggested that Cy homozygote be lethal in embryo period. These results will provide some helpful information to investigate molecular mechanism of curly wings in the further study.

Genetic diversity and relationship of Yunnan native cattle breeds and introduced beef cattle breeds.

In this study, random amplified polymorphic DNA (RAPD) analysis was used to estimate genetic diversity and relationship in 134 samples belonging to two native cattle breeds from the Yunnan province of China (DeHong cattle and DiQing cattle) and four introduced beef cattle breeds (Brahman, Simmental, MurryGrey, and ShortHorn). Ten primers were used, and a total of 84 bands were scored, of which 63 bands (75.0%) were polymorphic. The genetic distance matrix was obtained by proportions of shared fragment. The results indicate that the Yunnnan DeHong cattle breed is closely related to the Brahman (Bos indicus), and the Yunnan DiQing cattle breed is closely related to the Simmental, ShortHorn, and MurryGrey (Bos taurus) breeds. Our results imply that Bos indicus and Bos taurus were the two main origins of Yunnan native cattle. The results also provide the basic genetic materials for conservation of cattle resources and crossbreeding of beef cattle breeds in South China.

Effects of marker-assisted selection under different initial frequency of QTL favorable allele.

A ten-generation continuous selection experiment on a single trait in a closed population was carried out by stochastic simulation. It assumed that the trait was controlled by polygenes and a single autosomal bi-allelic marked quantitative trait locus (QTL). Individual breeding values were estimated through animal model marker-assisted best linear unbiased prediction (MB-LUP), and breeding animals were selected according to their breeding values. The effects of three levels initial frequencies of QTL favorable allele on marker-assisted selection (MAS) were studied. The results showed that it would gain higher genetic response when implementing MAS on those traits with lower initial frequency of QTL favorable allele. When the initial frequency of QTL favorable allele was low, although the generation number required for fixing QTL favorable allele in the population would be lengthened, its frequency would be increased faster. However, the initial frequency of QTL favorable allele had little effects on the inbreeding rates.

Primary factors affecting the evaluation accuracy of animal model MBLUP.

Marker-assisted best linear unbiased prediction (MBLUP) is one important method of implementing marker-assisted selection (MAS). The computer stochastic simulation method was used to study the effects of heritability of trait, QTL variance and map distance between two adjacent markers on the evaluation accuracy of animal model MBLUP. With the higher heritability, the smaller QTL variance and the shorter map distance between two adjacent markers, the evaluation accuracy of animal model MBLUP would be increased. On the contrary, the evaluation accuracy of animal model MBLUP would be decreased when the heritability was lower, QTL variance was larger and map distance between two adjacent markers was longer.

[Primary analysis of mitochondrial DNA D-loop region sequence in Baoshan pig].

To investigate the genetic diversity and genetic data of Baoshan pig in Yunnan province,the mitochondrial DNA D-loop hypervariable segment I sequences 15 363 approximately 15 801 (438 bp) in 19 individuals of Baoshan pig were sequenced. Ten mitochondrial haplotypes were identified in the samples, with 8 sites showing polymorphism, which were 5 T/C and 1 G/A transitions, 1 G/C and 1 A/T transversions. The contents of A,T,G and C were 35.4%,26 9%,13.2% and 24.5%,respectively. The content of A+T (62.3%) was significantly higher than that of G+C (37.3%). It will be of importance to conservation and sustainable utilization in Baoshan pig.