分子时代产前筛查和产前诊断技术和理念的变迁及发展

最初的产前诊断主要针对染色体非整倍体,随着遗传学检测技术的进展,越来越多的遗传性疾病可以在产前得到诊断,包括致病性拷贝数变异、单基因病、单亲二体等,产前遗传学检测从细胞遗传学时代进入到分子时代.随着cfDNA(cell-free DNA)检测迅速整合进入产前筛查领域,产前筛查也从基于生化指标的母血清学筛查时代进入到分子时代,很多单基因遗传病也可以通过扩展型携带者筛查被检出.技术的进步极大地促进了学科的发展,同时也极大地改变了人们的理念以及对产前筛查和产前诊断的认知.     

中国遗传咨询网——我国首个在线遗传咨询与遗传教育网站的开发

随着互联网的普及, 网络用户已习惯从网上获取相关资讯, 包括求医问药。由于我国的临床遗传学体系尚未完全建立, 许多遗传病患者或遗传咨询者无法得到较为专业的知识和咨询服务。为此, 建立了中国首个提供常见遗传病科普和网上遗传咨询服务的公益性网站—中国遗传咨询网(http://www.gcnet.org.cn)。该网站主要介绍遗传病的基本知识以及常见遗传病的一般情况、临床表现、诊断与防治方法、遗传方式与遗传咨询要点等。通过组织国内外50多名遗传咨询医师或医学遗传学专家, 就咨询者关心的问题, 进行一般性咨询答复, 或指导咨询者就诊。在线遗传咨询是网络时代的一种新型的方式。该网站的运行在一定程度上弥补了我国现有遗传咨询工作的不足, 有助于推动我国临床遗传学、遗传教育和人口与健康事业的发展。     

人类遗传病的携带者

携带者是遗传学中 1个较常见且很重要的名词。不同版本的遗传学给其下的定义不尽相同。比如 ,携带者就是基因型为杂合体的个体 ,或者是带有隐性致病基因而不发病的个体为携带者等等。实际上所谓携带者即是带有致病基因或异常染色体而表现型正常的个体。因此根据这一定义 ,携带者一般包括以下几种情况 :1)带有 ·隐性致病基因的携带者。如白化病、苯丙酮尿症的致病基因携带者 ,其基因型为 Aa带致病基因而表现型正常。两个基因型相同的携带者婚配就可能生出患儿 ,其子女发病风险为 1/ 4。若母亲是 X连锁隐性致病基因的携带者 ,则生下男孩将有…     

第24届国际生物学奥林匹克竞赛试题 理论Ⅱ-4

正问题35本题涉及一个家族中3位男性成员(A、B和C)进行的遗传咨询情况。下图展示该家族的一个遗传谱系,患遗传病X(黑色)和遗传病Y(灰色)的个体已被标出。其中遗传病X极其罕见,而导致遗传病的Y等位基因则在人群中占有6%的比例。指出下面的论述正确还是错误:A.个体B一定是遗传病X的携带者B.个体C不会是遗传病Y的携带者C.如果个体A与一个没有血缘关系也没患病     

荷斯坦奶牛脊柱畸形综合征的研究进展

荷斯坦奶牛脊柱畸形综合征是近年新发现的一种常染色体隐性遗传病,该病对纯合子胎儿是致死性的。当荷斯坦牛的育种核心群中携带者达到一定比例,脊柱畸形综合征就会对奶业造成巨大损失。文章综述了脊柱畸形综合征的主要症状和影响、致病基因及检测方法的研究进展以及我国潜在的荷斯坦奶牛脊柱畸形综合征携带者的状况。     

多个遗传标记情形下的RFLP的可诊断率估计

限制性酶切片段长度多态性(RFLP)作为共显性的遗传标记,已广泛应用于遗传病的产前诊断。为评价各遗传标记的适用性,本文给出了在多个遗传标记情形下的RFLP的可诊断率的估计方法,即在使用若干个遗传标记时,群体中可被诊断后代罹病与否的婚配类型的比例的估计方法,包括致病基因为常染色体显性、常染色体隐性、X连锁显性和X连锁隐性的情况,并认为增加遗传标记的个数和选择具较多等位基因的遗传标记,是提高产前诊断可诊断率的有效途径。同时,根据各遗传标记在群体中的多态性分布,可估计各遗传标记及其各种不同组合的可诊断率,以此选择在该群体中最为适合的遗传标记或其组合,以指导RFLP在产前诊断中的应用。     

集合论思想在生物学教学中的应用初探

集合是高中数学必修教材中的一章内容 ,它涉及交集、并集、补集、子集和全集等基本概念的理解和应用。集合图形一般用圆或椭圆来表示。在中学生物学教学中 ,根据具体情况来合理运用集合思想 ,能收到事半功倍的教学效果。1　运用集合方法巧解遗传几率计算题例 1,下面是某家系的遗传系谱图。家庭成员中有的患丙种遗传病 (设显性基因为 B,隐性基因为 b) ,有的患丁种遗传病 (显性基因为 A,隐性基因为 a)。现已查明 - 6不携带致病基因。问 :1)丙种遗传病的致病基因位于染色体上 ;丁图 1种遗传病的致病基因位于染色体上。2 )写出下列两个体的基…     

RFLP诊断方法的改进

RFLP(限制性片段长度多态)技术应用于遗传病的诊断始于1981年。在十年时间里,这一基因诊断技术和分析方法不断得到发展和改进。随着越来越多的致病基因和连锁DNA多态片段的分离和克隆,该技术在分析缺陷基因性质,携带者检出和产前诊断等方面将发挥重要作用.然而,RFLP技术复杂,耗费时间和费用较大,使其向临床推广应用面临很大局限性。因此,基因诊断的方法简化和技术改进大有必要。1985年首创的多聚酶链     

白化病的遗传流行病学研究

本文应用分离分析和血缘分析方法,对山东省１００余万人群遗传病调查中发现的３７个白化病核心家系进行了分析。结果表明：白化病存在遗传异质性,为多基因常染色体隐性遗传,最小基因数为８,平均基因频率为０．００２３,群体中致病基因携带者频率为０．０３８３;近亲结婚大大提高白化病的患病率。     

问：遗传病有哪些特点？

问：遗传病有哪些特点？答：遗传病是指由于体内遗传物质的改变或缺陷而引起的疾病,可分为单基因遗传病、多基因遗传病和染色体病,一般具有四大特点。（ｌ）家族性这是指排除那些共同环境因素或传染引起的情况外,某类疾病在患者家族中的发病率比一般人高。不一定代代相...     

心理治疗模式遗传咨询的工作重点及基本程序

心理治疗模式遗传咨询的工作重点及基本程序均有别于以往的遗传咨询模式。在这一模式中, 工作重点不再是单纯解决咨询者所遇到的生理问题, 而是要同时解决其所遇到的心理问题。其中由卡尔·罗杰斯提出的“以当事人为中心的疗法”在这一模式的咨询工作中占有重要的地位。由于工作重点由解决生理问题转移到心理问题, 心理治疗模式遗传咨询的工作程序亦需作相应的调整。这些程序大致可分为7个阶段: (1)首次接触; (2)相互介绍; (3)对咨询议程达成共识; (4)采集家族史; (5)告知并解释医学及遗传学信息; (6)结束咨询; (7)咨询后工作。     

Familial Creutzfeldt-Jakob Disease: Case report and role of genetic counseling in post mortem testing

Here we present a case of an asymptomatic 53-year-old woman who sought genetic testing for Familial Creutzfeldt-Jakob Disease (fCJD) after learning that her mother had fCJD. The patient's mother had a sudden onset of memory problems and rapidly deteriorating mental faculties in her late 70s, which led to difficulties ambulating, progressive non-fluent aphasia, dysphagia and death within ～1 y of symptom onset. The cause of death was reported as “rapid onset dementia.” The patient's family, unhappy with the vague diagnosis, researched prion disorders online and aggressively pursued causation and submitted frozen brain tissue from the mother to the National Prion Disease Surveillance Center, where testing revealed a previously described 5-octapeptide repeat insertion (5-OPRI) in the prion protein gene (PRNP) that is known to cause fCJD. The family had additional questions about the implications of this result and thus independently sought out genetic counseling.

?While rare, fCJD is likely underdiagnosed due to clinical heterogeneity, rapid onset, early non-specific symptomatology, and overlap in the differential diagnosis of Alzheimer disease and Lewy body dementias. When fCJD is identified, a multidisciplinary approach to return of results that includes the affected patient's provider, genetics professionals, and mental health professionals is key to the care of the family. We present an example case which discusses the psychosocial issues encountered and the role of genetic counseling in presymptomatic testing for incurable neurodegenerative conditions. Ordering physicians should be aware of the basic issues surrounding presymptomatic genetic testing and identify local genetic counseling resources for their patients.     

A missense mutation (His42Arg) in the T-protein gene from a large Israeli-Arab kindred with nonketotic hyperglycinemia

Nonketotic hyperglycinemia (NKH) is caused by a mutation in the genes encoding the components of the glycine cleavage multi-enzyme system. More than 80% of the patients have defects in the gene encoding P-protein, whereas the rest of the patints have defects in the gene encoding T-protein. We have found a large Israeli-Arab kindred with NKH. At least 14 children were affected, and all the patients had seizures and respiratory failure within 2 days after birth. Enzymatic analysis revealed that T-protein activity was deficient in the liver specimen from one propositus. We screened this family for a mutation in the protein-coding region and exon/intron boundaries of T-protein gene by direct sequencing analysis. A missense mutation was found in exon 2; this resulted in an amino acid substitution from histidine to arginine at position 42 (H42R). Histidine 42 is conserved in human, bovine, chicken, pea, and Escherichia coli, suggesting that it has an important role in catalytic functions. Genotype analyses of 26 family members confirmed that the homozygous H42R mutation was completely associated with the onset of NKH. The availability of DNA testing facilitates the prenatal diagnosis of NKH and the identification of carriers, which is necessary for genetic counseling in the affected families. Received: 28 October 1997 / Accepted: 6 January 1998     

Disclosure of genetic information to relatives in Israel: between privacy and familial responsibility

This article presents findings from a large quantitative-based study conducted in Israel in eight genetic clinics across the country regarding patients’ attitudes to disclosure of genetic information to relatives. The study examines the similarities and differences between the two largest groups who visit genetic clinics in Israel – for prenatal screening and for carrier testing for cancer. It was found that the overall rate of intention to inform relatives was high. It was also found that respondents in the cancer group expressed a more familial-based approach than those in the prenatal screening group. In addition, a relatively high rate of non-disclosure was found in the prenatal screening group as compared to the cancer group. These findings are significant in light of a widespread wish in Israeli society to give birth to a child without a disease or disability. A reconsideration of current practices and guidelines in this area is therefore required.     

Pediatric perspective on prenatal counseling for myelomeningocele

BACKGROUND: Over the past 35 years, advances in the prenatal diagnosis of spina bifida using ultrasound and laboratory testing have increased the number of patients seeking prenatal counseling. METHODS: Traditionally, this counseling has been provided by practitioners with little direct experience in the care of individuals with spina bifida across their life span. RESULTS: Physicians experienced in the care of children with spina bifida are able to provide information that is not available from other sources. CONCLUSIONS: This review provides a broad overview of many of the issues encountered during prenatal counseling sessions and emphasizes the additional value of the pediatric perspective during the process of informed decision making or preparation for an the birth of an affected child.     

Report on the Moscow symposium on biological research in schizophrenia

Abstract

Genetic counseling, second trimester amniocentesis, reliable techniques for analyzing fetal amniotic fluid and selective abortion together have the potential to prevent a variety of serious birth defects. Advances in technique and/or changing patterns of childbearing may place a large number of women in age groups where genetic counseling programs are recommended. However, attitudes toward abortion may be a critical variable in ascertaining the potential of genetic counseling programs to reduce birth defects. If opposition to abortion is based on a moral commitment, greater awareness of genetic counseling programs will lead to opposition to these programs. If attitudes toward abortion are based upon an evaluative process, such opposition is less likely to occur. Using a sample of women from the Rochester, New York, area (N = 1,616) whose attitudes toward abortion match U.S. estimates, we find that the greater the knowledge about prenatal screening, the less prevalent are attitudes opposed to abortion in circumstances necessary for birth defect reduction. This relationship holds when controlled for religion and family size. We conclude that educational and counseling programs concerning the potential benefits of prenatal screening are unlikely to arouse opposition to these programs.     

A novel mutation in EXT2 gene in a Chinese family with hereditary multiple exostoses

Hereditary multiple exostoses (HME) is an autosomal-dominant disorder characterized by the presence of bony outgrowths on the long bones. In this report, we describe a Chinese family with HME. Linkage analysis and mutation detection were performed. Linkage with the EXT2 was established in this family. A novel mutation, EXT2 c239-244delG, was identified. Mutation analysis in a family with HME allows for genetic counseling and prenatal diagnosis.     

Pelizaeus-Merzbacher disease: detection of mutations Thr181----Pro and Leu223----Pro in the proteolipid protein gene, and prenatal diagnosis.

A family with an apparent history of X-linked Pelizaeus-Merzbacher disease presented for genetic counseling, requesting carrier detection and prenatal diagnosis. RFLP analysis using the proteolipid protein (PLP) gene probe was uninformative in this family. A prenatal diagnosis on a chorionic villus sample (CVS) was carried out using single-strand conformation polymorphism (SSCP) analysis of a variant in exon 4 of the PLP gene. The fetus was predicted to be unaffected. Sequencing of the exon from the CVS, the predicted-carrier mother, and the obligate-carrier grandmother revealed an A-to-C change at nucleotide 541 in the two women but not in the fetus. As this change results in a Thr-to-Pro change at amino acid 181 in a region of the gene predicted to be part of a transmembrane segment, it was concluded that this was the mutation causing the disease in this family. In addition, in a second family, an exon 5 variant band pattern on SSCP analysis was shown by sequencing to be due to a T-to-C change at nucleotide 668. This results in a Leu-to-Pro change in a carrier mother and in her two affected sons. These results provide further examples of mutations in PLP that cause Pelizaeus-Merzbacher disease and illustrate the value of SSCP in genetic analysis.     

Carrier screening for Gaucher disease in couples of mixed ethnicity

With the advent of mutational analysis for Gaucher disease, carrier screening has been incorporated into many Jewish genetic disease screening programs. Frequencies and mutations for Gaucher disease in non-Jewish populations are less well established and the detection rate of carriers are lower. Testing is problematic for resolving residual risk in a couple of mixed ethnicity. We report the testing choices made by 20 consecutive couples of mixed ethnicity where the Ashkenazi Jewish partner was identified to be a Gaucher disease gene carrier. Carrier studies of the non-Jewish partner were elected as follows: DNA studies alone, 5 (25%); enzymatic assay, 2 (10%); both, 6 (30%); no carrier studies, 7 (35%). Of the 7 couples not electing carrier studies, one was not in a pregnancy and 6 elected prenatal diagnosis in lieu of parental testing by enzymatic analysis of amniocytes. One couple elected parental carrier studies as well as prenatal diagnosis. All couples electing prenatal Gaucher determination had amniocentesis for other indications as well (4, advanced maternal age; 4, parental anxiety). We conclude that Gaucher screening is feasible for couples of mixed ethnicity if appropriate counseling and testing are offered.     

New chromosomal syndrome: Miller-Dieker syndrome and monosomy 17p13

Summary The Miller-Dieker Syndrome (MDS) consists of lissencephaly, characteristic facies, pre- and postnatal growth retardation, plus various other birth defects. Autosomal recessive inheritance has been presumed based on four reported families with two or more affected siblings. We present substantial evidence that monosomy 17p13.3 causes the MDS phenotype. This includes two patients with ring chromosome 17, one patient with a de novo 17p13 deletion, and one patient with monosomy 17p due to an unbalanced 7p; 17p translocation. We report the first prenatal diagnosis of MDS in a 20-week fetus from this latter family. Additionally, we report a balanced translocation between chromosome 17 and different autosomes (8, 12, and 15) in three of the four familial cases of lissencephaly. The finding of a chromosomal basis for this presumed autosomal recessive disorder significantly alters genetic counseling and makes prenatal diagnosis possible in some families.United States Air Force Medical Corps