GENETICS OF THE PATERNAL SEX RATIO CHROMOSOME

PSR(父性比)是B染色体中的一个额外染色体。 寄生蜂。它是通过精子遗传的，但 然后导致父系染色体浓缩成染色质团 在第一次卵裂分裂之前。父亲的染色体是 最终丢失，但PSR染色体幸存下来并被传递到 下一代。正常情况下，雄性来自未受精(单倍体)。 这种黄蜂从受精(二倍体)的卵子中获得雌性的卵子。 因此，PSR的作用是将二倍体雌卵转化为单倍体卵子。 它们会发育成PSR雄性。 这一制度之所以重要，有两个原因。首先，PSR是一种离散的基因 导致父系染色体凝聚和失活的因素 在受精卵的有丝分裂过程中。因此，这是一个易于管理的系统。 目的：研究染色体印迹和染色体失活的遗传学。 其次，PSR是“自私”遗传因素的最极端的例子 描述得很清楚。因此，对PSR的遗传学研究将增加我们的 了解这些元素是如何演变和发挥作用的。研究将是 承诺回答两个问题。(1)人的遗传结构是什么 PSR染色体？以及(2)它是如何引起超凝结的？ 父亲的染色体？这些研究是便利的，因为(A)我们有 含有PSR特异性DNA的重组克隆可用作标记 通过缺失分析确定染色体的特征，(B)基因(S) 负责在特定区域发生的超凝结(SPC) PSR染色体(可以删除)和(C)遗传学实验表明 这些基因有时会在精子发生过程中起作用。以下是 将进行研究计划。遗传学、细胞遗传学和分子生物学 实验将确定PSR染色体的结构并定位 SPC基因(S)的其他实验将更精确地确定时间 父系染色体的PSR修饰和寻找可能的 正常染色体上PSR作用的靶点。一个cDNATES文库 将进行筛选以识别PSR特定的成绩单，并确定 这些与spc基因(S)相对应。 除了提供对染色体失活机制的基本见解 和“自私”DNA的遗传学，PSR染色体可能有 作为昆虫生防剂的重要应用 对人体健康和营养有害。

Psr (paternal sex ratio) is a supernumerary (of B) chromosome in the parasitic wasp. Nasonia vitripennis, which is inherited through sperm but then causes the paternal chromosomes to condense into a chromatin mass prior to the first cleavage division. The paternal chromosomes are eventually lost, but the psr chromosome survives and is transmitted to the next generation. Normally males are derived from unfertilized (haploid) eggs while females are derived from fertilized (diploid) eggs in this wasp. Thus, the affect of psr is to convert diploid female eggs into haploid eggs which develop into psr males. The system is important for two reasons. First, psr is a discrete genetic element that causes paternal chromosome condensation and inactivation during mitosis in the fertilized eggs. It is therefore a tractable system to study genetics of chromosome imprinting and chromosome inactivation. Second, psr is the most extreme example of a "selfish" genetic element so far described. Therefore, genetic studies of psr will increase our understanding of how these elements evolve and function. Research will be undertaken to answer tow questions. (1) What is the genetic structure of the psr chromosome? and (2) How does it cause supercondensation of the paternal chromosomes? These studies are facilitated because (a) we have recombinant clones containing psr specific DNA which can be used as markers to characterize the chromosome by deletion analysis, (b) the gene(s) responsible for supercondensation (spc) occur in a specific region of the psr chromosome (which can be deleted) and (c) genetic experiments indicate that these genes act sometime during spermatogenesis. The following research program will be undertaken. Genetic, cytogenetic and molecular experiments will determine the structure of the psr chromosome and locate the spc gene(s) Other experiments will determine more precisely the timing of psr modification of the paternal chromosomes and search for possible target sites of psr action on the normal chromosomes. A cDNA testes library will be screened to identify psr specific transcripts and to determine if these correspond to the spc gene(s). Besides providing basic insight into mechanisms of chromosomal inactivation and the genetics of "selfish" DNA, the psr chromosome could have significant applications as a biological control agent of insects deleterious to human health and nutrition.