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Abstract: Molecular identification of human externally visible characteristic （EVC）, which is also called forensic DNA phenotyping （FDP）, can serve as a "molecular witness" when the routine investigations can not determine the identity of a criminal and the DNA database find no match after comparison. FDP could assist in investigation of cases by inferring the externally visible phenotypic characteristics from DNA obtained from the biological materials left at crime scenes, or unknown corpses. In the last few years, studies on the selection of EVC related molecular markers have been reported frequently and some of the EVCs could already be inferred with a certain accuracy, such as hair color and iris color. Further fundamental research on molecular genetics of human external phenotypic characteristics, as well as the continuous innovation on molecular biological technology would promote the rapid development of DNA molecular identification of human phenotypic characteristics., Competing Interests: The authors of this article and the planning committee members and staff have no relevant financial relationships with commercial interests to disclose., (Copyright© by the Editorial Department of Journal of Forensic Medicine.)

Mice are the most commonly used mammalian model. The coat colors of mice are typical Mendelian traits, which have various colors such as white, black, yellow and agouti. The inheritance of mouse coat color is usually stated as an example only in teaching the knowledge of recessive lethal alleles. After searched the related literatures and summarized the molecular mechanisms of mouse coat color inheritance, we further expanded the application of this example into the introduction of the basic concepts of alleles and Mendelian laws, demonstration of the gene structure and function, regulation of gene expression, gene interaction, epigenetic modification, quantitative genetics, as well as evolutionary genetics. By running this example through the whole genetics-teaching lectures, we help the student to form a systemic and developmental view of genetic analysis. At the same time, this teaching approach not only highlights the advancement and integrity of genetics, but also results in a good teaching effect on inspiring the students' interest and attracting students' attention.

The "black bone and muscle" is cardinal melanin trait of black bone sheep. The black bone sheep and the native sheep in Lanping and Luomuni sheep were chosen as materials for the measurement of TYR activity of blood and melanin content of tissues and organs. Moreover, we compared characteristic structure of melanin of black bone sheep with silky fowls. The results showed as follows: TYR activity was significantly different between black and non-black bone sheep (P<0.05); the total character of infrared spectrum (IR) of melanin of black bone sheep resembled silky fowls; and melanin was eumelanin. We firstly cloned exon1 667bp sequence of TYR gene and determined TYR gene polymorphism of black and non-black bone sheep by PCR-RFLP. Compared with sequence of TYR gene of non-black bone sheep, there were two nucleotide mutation sites in exon1 of black bone sheep, located in No.64 and No.154 amino acid codons, respectively; but they were synonymics mutation. We designed restriction site in codon 64 and check up TYR gene polymorphism. The result showed the mutation site together with the close linked gene influenced melanin trait deposition. It suggests there should be functional mutation related with melanin trait. Furthermore, there was significant correlation between TYR gene polymorphism and coat color of sheep (P<0.01), indicating TYR could influence synthesis of coat color of sheep.

Canines were domesticated approximately 10,000 years ago. The various environmental conditions and selective breeding resulted in abundant diversity of coat colors in domestic canines. Many canine coat colors are affected by melanocortin 1 receptor (MC1R). MC1R genes are homologous among different species. This article reviews the studies on MC1R polymorphism in the domestic canine. We also constructed a phylogenetic tree of MC1R genes by comparing the canine gene with those from nine representative mammalian species. Results show the gene phylogenetic tree accorded with Taxonomy of the ten mammals in the main.

The classical White (I) locus is one of the important pig coat color hereditable loci,which is homologous to KIT gene. In this study,PCR-RFLP and PCR-SSCP analysis were commanded on the Intron 17 and 18 nucleotide sequences of KIT gene. The tested results showed that the substitution mutation (G-->A) of Intron 17 was found in white pigs, including Wuzhishan pigs (white), Landrace and Large White,and its genotype (AB) frequency was 1.1 and 0.8 respectively. The genotype frequency was uniformly 0 in the other native pig breeds. Similarly,the deleted mutation (AGTT) of Intron 18 was also found in the same white pigs,its genotype (,AA) frequency was 1.1 and 0.93 separately,while in the other native pig breeds was 0. Accordingly it was considered that KIT gene was an important factor regulating the white coat color genotype, and the classical I locus (KIT gene) was epistatic to the other genetic coat color loci. On the other hand,although the native pig breed Rongchang Pig is similar to Landrace and Large White in phenotype (white coat color), the mutation status found in them was absolutely distinct. So it is presumed that the coat color genetic system of Chinese native pig breeds was different from that of imported breeds.

The study of the molecular regulation mechanism of melanin synthesis during animal development has become a new focus recently . The synthesis and production of melanin during animal development are regulated by many genes. This paper summarized the molecular function mechanism of melanocortin-1-receptor (MC1R) gene and the relationship between the consequences of polymorphic variation of the gene and melanin traits, in addition to summarized the identification and mutation of MC1R gene in birds. Furthermore, the melanin synthesis mechanism in birds is also discussed here.

In order to detect the polymorphism of T105A in MC1R gene in dogs and to analyze the relationship between the genetic polymorphisms and phenotypes of dog coat color, the blood samples of 111 cross-breed dogs were taken and their genomic DNAs were extracted. The phenotypes of dog coat color were recorded. The T105A locus of MC1R gene in the canine was detected through the technology of PCR-RFLP. Furthermore, the polymorphic fragments at T105A were sequenced. The relationships between the polymorphism of T105A and coat color trait were analyzed by the statistical methods of bivarate correlation analysis. By the method of PCR-RFLP, the T105A polymorphism was found with two alleles A and B and three genotypes AA, AB and BB. The frequencies of two alleles were 72.97% and 27.03%, respectively. The heterozygosity of T105A locus was 0.39. The frequencies of three genotypes were 55.86%, 34.23% and 9.91%, respectively. According to the results of sequencing, one base change from G to A at the position 105 was found at T105A locus and it altered amino acid at the position 105 from alanine to threonine. According to the statistical analysis, no significant association between the polymorphism of MC1R gene and the coat color was found and the result may be due to the differences of genetic background. Further research on MC1R gene should be done in pure breed dogs.

Using brother-sister inbreeding with forced heterozygosity to breed a new segregating inbred strain which carry mutant hairless gene. Then, genetic monitoring was conducted by the skin grafting test, coat color test and biochemical marker analysis, and its basic biological characteristics were studied with corresponding methods. The Results are that the Yuyi Hairless Mice (YYHL) with unique biological characteristics have been bred successfully and have progressed to 30th generation since 1991. Thirteen biochemical markers loci on nine chromosomes coding biochemical markers measured with electrophoresis were all homogenous. The skin grafting test showed that no dropping graft was found during 100 days after transplanting, implying the YYHL was of isohistogeneicity. Analysis of coat color genes indicated that the hair color of first generation hybrid crossed between YYHL and DBA/2 was all agouti suggesting that the coat color genes of the YYHL were homogenous. The gene type is AABBccDD. All these showed that the YYHL have been an inbred strain reaching the international standards.