OBJECTIVETo understand the mutational patterns and mechanism of short tandem repeats(STRs).

METHODSThe DNA samples of 19 parent-child pairs with mutations in three loci (FGA, D12S391, and D11S554) were genotyped by silver staining on STR. Alleles to be sequenced were excised from gels, reamplified by PCR, and purified. Sequencing was performed by use of cycle sequencing.

RESULTSThere were 18 out of 19 pedigrees in which the 'new' alleles gained or lost a single repeat (8 gains, 7 losses, and 3 being indistinguishable). Only one pedigree lost two repeats. In the 19 pedigrees, there were 13 pedigrees whose 'new' alleles came from fathers, 3 from mothers, 3 from either father or mother. The ratio was 4 1 between fathers and mothers. The mutation of three STR loci occurred in the long, uninterrupted tetranucleotide repeat regions ('CTTT' in FGA, 'AGAT' in D12S391, and 'AAAG' in D11S554).

CONCLUSIONSingle- step mutations accounted for 95% of STR mutation events in these three loci: FGA, D12S391, and D11S554. The rest were double step mutations. There was no insertion or deletion of an incomplete repeat in any of the pedigrees. The mutation was mainly caused by fathers. The long, uninterrupted tetranucleotide repeats in these three loci might be susceptible to mutation.

Alleles ; Base Sequence ; DNA ; chemistry ; genetics ; DNA Mutational Analysis ; Female ; Gene Frequency ; Genotype ; Humans ; Male ; Microsatellite Repeats ; genetics ; Mutation ; Nuclear Family ; Tandem Repeat Sequences ; genetics

The connotation of theory of "kidney dominating bone" is quite clear,but theory of "Shaoyang dominating bone " has an obscure meaning.The causes are analyzed as followings:insufficient explanation in Huangdineijing (Huangdi's Internal Classic),controversial original texts,unclear clinical indications and no unified opinion on theoretical interpretation made by later physicians.The theory of "kidney dominating bone" stresses on growing of bone,refers to a single and clear meaning.However,the theory of "Shaoyang dominating bone" stresses on the using of bone,including liver blood,kidney essence,qi and blood,meridians and the coordination of bones and muscles,is a wide range of theoretical category which is difficult to be clarified.It is possible that the ancients intended to make an obscure meaning of the theory of "Shaoyang dominating bone".