DNA construction of chromosome 21 and the study of Down syndrome.

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1) Eleven anonymous DNA segments and two cDNA which were cloned from chromosome 21 were assigned in the chromosome by in situ hybridization. These anonymous DNA segments are single copy inserts and had been screened for restriction fragment length polymorphism (RFLP) in the DNA of unrelated humans. Among eleven probes, five were assigned to 21q22.3, two to 21q11, and the four remaining genes were assigned to 21q11-q21, 21q21, 21q21-q22.1, and a centromeric region. One of cDNAs was assigned to 21q21 and the other was to 21q22.3. Five anonymous DNA segments and one cDNA probe, therefore, were assigned to the critical region for phenotype expression of Down syndrome. These may become very important for the study of pathogenesis.2) Pulse field gel electrophoresis were applied to study a large DNA molecule cloned by means of yeast artificial chromosome (YAC) vectors. This is a preliminary report of analysing chromosome 21 DNA construction. In the initial study, DNA inserts are short as about six thousand base pairs , so that we must make effort to get more sufficient size of probes. Molecular study of chromosome 21 is necessary more for the disease.