1. Genetic variation in the chicken MC1R gene was analysed through bioinformatic methods after polymerase chain reaction (PCR) amplification and sequencing of the coding region of MC1R gene from 5 different populations with 4 plumage colours (black, grey plumage with black spots, yellow plumage with black spots, red). 2. A total of 11 novel variations were detected in Hebei chickens, of which 8 were non-synonymous. Allele distribution analysis showed that the wild-type e(+) (Brown Leghorn) allele was mainly found in Hy-Line Brown and Lohmann Brown, the dominant Extended black E(AY220304) allele was mainly found in Hebei chicken with black plumage, whereas the Buttercup (e(bc)) allele was rare. 3. Nucleotide diversity (π) within each colour strain of Hebei chickens (0·0047-0·0052) was significantly greater than that of Hy-Line Brown (0·0024) or Lohmann Brown (0·0043). 4. The results indicate that there is abundant polymorphism in the MC1R gene, especially in Hebei chicken, which was associated with its rich plumage colour diversity.

ABSTRACT. Breast cancer is among the most common causes of cancerrelated death in women worldwide. Previous studies have demonstrated an association between prolonged estrogen exposure and increased risk of breast cancer. Uridine 5'-diphospho-glucuronosyltransferase 1-1 (UGT1A1) plays a significant role in the detoxification of estrogens. Two major genetic polymorphisms have been identified in the UGT1A1 locus. UGT1A1*28 has been previously linked to increased risk of breast cancer. The aim of this study was to elucidate the possible correlation between UGT1A1*6, a single nucleotide polymorphism causing a Gly71Arg substitution, and breast cancer susceptibility. Forty-six women diagnosed with breast cancer, 15 patients with gastrointestinal cancer, and 13 healthy women were recruited to this study. The genotype in the polymorphic UGT1A1 locus was determined by DNA sequencing. The frequency of each genotype was compared among the three groups. The frequency of the UGT1A1*6 allele was significantly higher in breast cancer and gastrointestinal cancer patients than that in healthy females (both P < 0.05). No significant associations were observed between the UGT1A1*6 polymorphism and estrogen receptor, progesterone receptor, HER-2 expression status, menstrual status, or metastasis (all P > 0.05). Therefore, the UGT1A1*6 polymorphism was deduced to be a risk factor for breast cancer in women of Han Chinese ethnicity. UGT1A1 may serve as a therapeutic target for the prevention and treatment of breast cancer and other estrogen-related diseases.