MOLECULAR ANALYSIS OF SOMATIC RECOMBINATION

各种类型的突变是罕见的事件，发生在所有 增殖细胞群。 那些影响生殖细胞的基因 由progenyY表达;影响体细胞的那些更多 神秘的，因此得到了相对较少的关注。 一些最早的证据表明，突变发生在哺乳动物 体细胞是细胞遗传学的：偶尔细胞分裂， 体外表现出染色体畸变，其中一些是 遗传的 某些罕见的癌症易感人类基因 已经发现了显微镜下可检测到的 畸变增加，布卢姆综合征（BS）是 样机 BS中的畸变类型类似于 在正常细胞中，除了它们的频率增加 细胞遗传学只提供了最广泛的建议， 自然发生的突变， 增殖体细胞。 这项工作建议采用重组 DNA技术来分析这些突变，包括 这是由重组事件造成的，在一定程度上， 定义它们。 将使用BS细胞作为实验模型 由于突变频率的增加，如图所示， 细胞遗传学 单个细胞的DNA（即，克隆人和 亚克隆）将使用 一组用于高度多态性基因座分布的分子探针 在整个基因组中， 培养的细胞来源于哪个个体。损失 杂合性和新等位基因的出现将标志着 DNA碱基序列改变的产生。 这些意见将补充 其他人则鉴定了人类癌症中存在的分子变化， 假设是，某些类型的突变发生在 二倍体，非肿瘤性BS细胞和正常细胞中， 频率较低的是构成第一步的变化， 肿瘤性转化

Mutations of various types are rare events that occur in all proliferating cell populations. Those affecting the germ line may be expressed by progenyY; those affecting somatic cells are more occult and therefore have received relatively little attention. Some of the first evidence that mutation occurs in mammalian somatic cells was cytogenetic: occasional cells dividing in vitro exhibits chromosome aberrations, some of which are heritable. Certain rare cancer-predisposing human genetic disorders have been discovered in which microscopically detectable aberrations are increased, Bloom's syndrome (BS) being the prototype. The types of aberrations in BS resemble those in normal cells, except for their increased frequency Cytogenetics has provided only the broadest suggestion of the nature of the mutations that occur spontaneously in proliferating somatic cells. The work proposed applies recombinant DNA technology to analyze these mutations, including those resulting from recombinational events, and to a certain extent to define them. BS cells will be used as the experimental model because of the increased frequency of mutations, as shown cytogenetically. DNA of single cells (i.e., of clones and subclones) of lymphoblastoid cells will be analyzed using a panel of molecular probes for highly polymorphic loci distributed throughout the genome that are heterozygous in the genome of the individual from whom the cultured cells had been derived. Loss of heterozygosity and the appearance of new alleles will signal the generation of DNA-base-sequence alterations. The observations will be complementary to those being made by others identifying the molecular changes present in human cancers, the hypothesis being that some type(s) of mutations occurring in diploid, non-neoplastic BS cells and in normal cells at a much lower frequency are the changes that constitute the first step in neoplastic transformation.