冈田氏绕眼果蝇核型研究初报

对冈田氏绕眼果蝇的三龄幼虫的神经节细胞的染色体进行了初步报道．结果表明,冈田氏绕眼果蝇体细胞染色体数目为２ｎ＝１２．常染色体５对,为正中或中部着丝粒染色体,Ｘ为端部着丝粒染色体,Ｙ为中部着丝粒染色体,但其染色单体紧紧靠在一起．此核型在果蝇科已知的核型中是少见的．     

中华涡蛛（Octonoba sinensis）的核型

报道了中华涡蛛的染色体数目，形态结构和性染色体组成，实验材料采自石家庄郊区交园。细胞学数据主要来自对胚胎细胞有丝分裂中期的观察。实验结果表明：中华涡蛛的染色体数目是；雄性体细胞为１７，雌性体细胞为１８。性别决定机制是ＸＯ型，Ｘ染色体是全部染色体中最长的一个，并且是唯一的亚中着丝粒染以体，其常染色体均为端或亚端着丝粒染色体。     

冈田氏绕眼果绳核型研究初报

对冈田氏绕眼果蝇的三龄幼虫的神经节细胞的染色体进行了初步报道。结果表明，冈田氏绕眼果蝇体细胞染色体数目为２ｎ＝１２。常染色体５对，为正中或中部着丝粒染色体，Ｘ为端站着丝粒染色体，Ｙ为中部着丝粒染色体，但其染色单体紧紧靠在一起。此核型在果蝇科已知的核型中是少见的。     

棕色田鼠减数分裂及精细胞染色体数目的研究

以棕色田鼠精母细胞的研究对象，观察减数分裂各时期染色体特征性变化，特别对精细胞染色体构成及数目进行了研究，结果表明，Ｘ型和Ｙ型精细胞均显著了染色体数目的多态性（２ｎ＝２４，２５，２６）可以认为这是造成棕色田鼠体细胞染色体数目多态性的原因之一。     

疏毛蘑芋染色体核型研究

本文首次报道了疏毛蘑芋Ａｍｏｒｐｈｏｐｈｌｌｕｓ ｓｉｎｅｎｓｉｓ Ｂｅｌｖａｌ的细胞染色体数目和核型,并与其近缘种蘑芋Ａ．ｒｉｖｉｅｒｉ Ｄｕｒｉｅｕ和白蘑芋Ａ．ａｌｂｕｓ Ｐ．Ｙ．Ｌｉｕ ｅｔ Ｊ．Ｆ． Ｃｈｅｎ的核型进行了比较。结果表明,该种的体细胞染色体数为２６,核型公式为２ｎ＝２６＝２２ｍ（２ＳＡＴ）＋４ｓｍ,属２Ａ型,其染色体相对长度组成为２ｎ＝２６＝１２Ｍ２＋１２Ｍ１＋２Ｓ。     

蜘蛛胚胎细胞染色体的初步研究

以蜘蛛发育早期胚胎为材料,对微蛛科四种蜘蛛的染色体进行了观察,其结果是:草间小黑蛛、隆背微蛛、难波微蛛三种蜘蛛的染色体数目均为:2n=24和26,食虫瘤胸蛛:2n=22和24,由此推断它们的性决定机制是X_1X_2O型。     

棕色田鼠减数分裂及精细胞染色体数目的研究

以棕色田鼠精母细胞为研究对象，观察减数分裂各时期染色体特征性变化，特别对精细胞染色体构成及数目进行了研究．结果表明，ｘ型和ｙ型精细胞均显示了染色体数目的多态性（２ｎ＝２４，２５，２６），可以认为这是造成棕色田鼠体细胞染色体数目多态性的原因之一．     

脓疮草复合体的染色体研究

国产脓疮草复合体五个种１２个居群的染色体核型：Ｐ．ｌａｎａｔａ四个居群分别为２ｎ＝２Ｘ＝１８＝１８ｍ,２ｎ＝２Ｘ＝１８＝１０ｍ＋８ｓｍ,２ｎ＝２Ｘ＝１８＝１６ｍ＋２ｓｍ及２ｎ＝２Ｘ＝１８＝１４ｍ＋４ｓｍ;Ｐ．ａｌａｓｃｈａｎｉｃａ四个居群分别为２ｎ＝２Ｘ＝１８＝１２ｍ＋６ｓｍ,２ｎ＝２Ｘ＝１８＝１６ｍ＋２ｓｍ,２ｎ＝２Ｘ＝１８＝１８ｍ及２ｎ＝２Ｘ＝１８＝１４ｍ＋４ｓｍ;Ｐ．ａｒｇｙｒａｃｅａ两个居群均为２ｎ＝２Ｘ＝１８＝１６ｍ＋２ｓｍ;Ｐ．ｋａｎｓｕｅｎｓｉｓ一个居群为２ｎ＝２Ｘ＝１８＝１４ｍ＋４ｓｍ;Ｐ．ｐａｒｖｉｆｌｏｒａ为２ｎ＝２Ｘ＝１８＝１４ｍ＋４ｓｍ．这些核型相对一致．     

川北细辛和祁阳细辛的核型研究

报道了２种细辛属植物－川北细辛和祁阳细辛的染色体资料。川北细辛体细胞染色体数目２ｎ＝２２,核型公式为Ｋ（２ｎ）＝２ｘ＝４Ｍ＋１４ｍ＋４ｓｍ。祁阳细辛体细胞染色体数目２ｎ＝２４,核型公式为Ｋ（２ｎ）＝２ｘ＝２Ｍ＋２０ｍ＋２ｓｍ。     

红豆杉离体培养染色体数变异与细胞多核现象

分别对在固体培养基上静止培养和在摇瓶、１０Ｌ及１００Ｌ生物反应器内悬浮培养的红豆杉茎尖和根尖离体细胞进行染色体数目观察,发现其染色体数目主要类型和亲本株相同,为２ｎ＝２４,且存在较大比例的染色体数目变异的细胞．还发现,离体培养红豆杉细胞有丝分裂间期存在多核现象．认为染色体数目的变异可能是红豆杉离体培养细胞紫杉醇产量不稳定的主要原因．     

A primitive Y chromosome in papaya marks incipient sex chromosome evolution

Many diverse systems for sex determination have evolved in plants and animals. One involves physically distinct (heteromorphic) sex chromosomes (X and Y, or Z and W) that are homozygous in one sex (usually female) and heterozygous in the other (usually male). Sex chromosome evolution is thought to involve suppression of recombination around the sex determination genes, rendering permanently heterozygous a chromosomal region that may then accumulate deleterious recessive mutations by Muller's ratchet, and fix deleterious mutations by hitchhiking as nearby favourable mutations are selected on the Y chromosome. Over time, these processes may cause the Y chromosome to degenerate and to diverge from the X chromosome over much of its length; for example, only 5% of the human Y chromosome still shows X-Y recombination. Here we show that papaya contains a primitive Y chromosome, with a male-specific region that accounts for only about 10% of the chromosome but has undergone severe recombination suppression and DNA sequence degeneration. This finding provides direct evidence for the origin of sex chromosomes from autosomes.     

刺獾蛛染色体的初步观察

报告了刺獾蛛（Ｔｒｏｃｈｏｓａｓｐｉｎｉｐａｌｐｉｓ）染色体数目、形态结构和性染色体组成     

Genetic evidence that a Y-linked gene in man is homologous to a gene on the X chromosome

The mammalian sex chromosomes are thought to be related to each other by sharing a common origin. That is, the X and Y chromosomes originally evolved from a pair of chromosomes that only differed at the locus determining sexual differentiation. For example, this evolutionary relationship is reflected during meiosis in chromosomal pairing between the tip of the human X chromosome short arm and the Y chromosome which presumably implies sequence homology. However, compelling genetic evidence for functional homology between the mammalian X and Y chromosome is lacking. We describe here the localization of a gene to the tip of the short arm of the human X chromosome and evidence for a related gene on the Y chromosome.     

Population structure of the human pseudoautosomal boundary

The mammalian sex chromosomes are composed of two genetically distinct segments: the pseudoautosomal region, where recombination occurs between the X and Y chromosomes, and the sex chromosome-specific parts. Between these two segments the human sex chromosomes differ by the insertion of an Alu element on the Y chromosome. We have surveyed the sequence variation in the boundary region using the polymerase chain reaction. Fifty seven Y and sixty X chromosomes from ten different human populations were analysed. The X chromosomes were found to be polymorphic at five positions in a 300-base-pair region. By contrast, all Y chromosomes were identical except for one distal polymorphism shared with the X chromosome.     

The pseudoautosomal boundary in man is defined by an Alu repeat sequence inserted on the Y chromosome

The Y chromosome, which in man determines the male sex, is composed of two functionally distinct regions. The pseudoautosomal region is shared between the X and Y chromosome and is probably required for the correct segregation of the sex chromosomes during male meiosis. The second region includes the sex-determining gene(s), the presence of which is necessary for the development of testes. The two regions have contrasting genetic properties: the pseudoautosomal region recombines between the X and Y chromosome; the Y-specific region must avoid recombination otherwise the chromosomal basis of sex-determination breaks down. The pseudoautosomal region is bounded at the distal end by the telomere and at the proximal end by X- and Y-specific DNA. We have found that the proximal boundary was formed by the insertion of an Alu sequence on the Y chromosome early in the primate lineage. Proximal to the Alu insertion there is a small region where similarity between the X and Y chromosomes is reduced and which is no longer subject to recombination.     

Repetitive DNA sequences from the X chromosome of the spiny eel (Mastacembelus aculeatus)

To investigate the characters of repetitive DNA sequence in the sex chromosomes of the spiny eel (Mastacembelus aculeatus), the X chromosomal library was screened and a family of repetitive sequence, consisting of Ma 1-Ma 6, was isolated. The fluorescence in situ hybridization (FISH) result confirmed that Ma 1 - Ma 5 dispersed over sex chromosomes and all autosomes, whereas, Ma 6 is sex chromosome-specific and distributed only on the C-band positive regions of X chromosome, and Ma 6 maybe the main components of the heterochromatic regions of X chromosome. This study provides additional information about the evolution of sex chromosomes in lower vertebrates such as fish.      

In the platypus a meiotic chain of ten sex chromosomes shares genes with the bird Z and mammal X chromosomes

Two centuries after the duck-billed platypus was discovered, monotreme chromosome systems remain deeply puzzling. Karyotypes of males, or of both sexes, were claimed to contain several unpaired chromosomes (including the X chromosome) that form a multi-chromosomal chain at meiosis. Such meiotic chains exist in plants and insects but are rare in vertebrates. How the platypus chromosome system works to determine sex and produce balanced gametes has been controversial for decades. Here we demonstrate that platypus have five male-specific chromosomes (Y chromosomes) and five chromosomes present in one copy in males and two copies in females (X chromosomes). These ten chromosomes form a multivalent chain at male meiosis, adopting an alternating pattern to segregate into XXXXX-bearing and YYYYY-bearing sperm. Which, if any, of these sex chromosomes bears one or more sex-determining genes remains unknown. The largest X chromosome, with homology to the human X chromosome, lies at one end of the chain, and a chromosome with homology to the bird Z chromosome lies near the other end. This suggests an evolutionary link between mammal and bird sex chromosome systems, which were previously thought to have evolved independently.     

大瓶螺（Ampullar ia gigas Spix）的核型分析

本文采用鳃及性腺组织制片法，分析大瓶螺染色体组型，结果表明，大瓶螺染色体为２ｎ＝２８，可配为１４对，除３、８、１２这３对为亚中部着丝点染色体外，其余皆为中部着丝点染色体，染色体长度呈连续递变，其中相对长度最长的１号染色体为１０．０９，最短的１４号染色体为５．１０，ＮＦ＝５６，全套染色体上未发现有次缢痕，随体及与性别有关的性染色体存在。     

Hypervariable telomeric sequences from the human sex chromosomes are pseudoautosomal

Pairing of human X and Y chromosomes during meiosis initiates within the so-called pairing region at the telomeres or the chromosome short arms. Using DNA from the Y chromosome we found sequence homology in the pairing region of the human X and Y chromosomes. This DNA is telomeric, contains repetitive sequences and is highly polymorphic in the population. The polymorphism has allowed family studies which show the sequences are not inherited as though linked to the sex chromosomes. This 'pseudoautosomal' pattern of inheritance points to an obligate recombination in the pairing region of the sex chromosomes during male meiosis.