DOCSLIB.ORG

Germline BRCA1 Mutations and Loss of the Wild-Type Allele in Tumors from Families with Early Onset Breast and Ovarian Cancer1

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Germline BRCA1 Mutations and Loss of the Wild-Type Allele in Tumors from Families with Early Onset Breast and Ovarian Cancer1 Vol. 1, 539-544, May 1995 Clinical Cancer Research 539 Germline BRCA1 Mutations and Loss of the Wild-Type Allele in Tumors from Families with Early Onset Breast and Ovarian Cancer1 Sofia D. Merajver,2 Thomas S. Frank, Junzhe Xu, revealed that only the disease-related allele of BRCAJ was Trinh M. Pham, Kathleen A. Caizone, present. These data strongly support the hypothesis that BRCA1 is a tumor suppressor gene. Pamela Bennett-Baker, Jeffrey Chamberlain, Jeff Boyd, Judy E. Garber, Francis S. Collins, INTRODUCTION and Barbara L. Weber Familial early onset breast/ovarian cancer is an autosomal Departments of Internal Medicine [S. D. M., T. M. P.], Pathology dominant disorder manifested as an increased susceptibility to [T. S. F.], and Human Genetics [J. C., P. B-B.], and the Human breast cancer starting in the third decade, with an 85% lifetime Genome Center [J. X., F. S. C.], University of Michigan, Ann Arbor, Michigan 48109; Dana-Farber Cancer Institute, Boston, risk. Breast adenocancinomas and ovarian cystadenoeancinomas Massachusetts 02115 [J. E. G.]; National Center for Human Genome are the predominant histological types. Mucinous ovarian can- Research, NIH, Bethesda, Maryland 20892 [F. S. C.]; and cens seem to be less common in hereditary breast/ovarian fam- Departments of Obstetrics and Gynecology [J. B.], Internal Medicine ilies (1), but in general the familial tumors are phenotypically [K. A. C., B. L. W.], and Genetics, University of Pennsylvania, Philadelphia, Pennsylvania 19104 indistinguishable from histologically matched sporadic tumors. Atypical hyperplasia, a premalignant lesion, has been found in one study to be more prevalent in families at increased risk for ABSTRACT hereditary breast cancer (2). The natural history of the tumors, The BRCA1 gene on human chromosome 17q21 is re- including detectability by radiographic and clinical means, ne- sponsible for an autosomal dominant syndrome of inherited sponsiveness to therapy, and overall prognosis for the patients early onset breast/ovarian cancer. It is estimated that based on stage at presentation appear to be indistinguishable women harboring a germline BRCAJ mutation incur an from age-matched controls (1). 85% lifetime risk of breast cancer and a greatly elevated Since 1990, it has been known that a single locus on risk of ovarian cancer. The BRCA1 gene has recently been chromosome 17q21, termed BRCAJ,3 is responsible for most isolated and mutations have been found in the germline of cases of hereditary early onset breast/ovarian cancer (3, 4). affected individuals in linked families. Previous studies of Approximately 67% of families with breast cancer diagnosed loss of heterozygosity (LOH) in breast tumors have been before age 45 years and 95% of families with breast/ovarian carried out on sporadic tumors derived from individuals cancer appear to be linked to BRCAJ. Easton et a!. (5) have without known linkage to BRCA1 and on tumors from recently reported that the penetrance, by age 70 years, is 87% linked families. Loss of large regions of chromosome 17 has (95% CI: 72-95) for breast cancer and 44% (95% CI: 28-56) been observed, but these LOH events could not be unequiv- for ovarian cancer. The ovarian cancer risk may be an ovenes- ocally ascribed to BRCA1. timate, however, because of a bias favoring ascertainment of We have studied 28 breast and 6 ovarian tumors from families with both breast and ovarian cancer. In addition, Fond families with strong evidence for linkage between breast et a!. (6) have reported a significant increase in the relative risks cancer and genetic markers flanking BRCAJ. These tumors for colon (4.11, 95% CI: 2.36-7.15) and prostate cancer (3.33, were examined for LOH using genetic markers flanking and 95% CI: 1.78-6.20) in BRCAJ mutation carriers. The BRCAJ within BRCAJ, including THRA1, D175856, EDH17B1, gene has recently been reported and disease-associated muta- EDH17B2, and D17S183. Forty-six percent (16/34) of tu- tions have been found in breast and breast/ovarian kindreds mors exhibit LOH which includes BRCA1. In 8 of 16 tumors (7-1 1). The study of tumors in linked families may help eluci- the parental origin of the deleted allele could be determined date how BRCAJ mutations lead to disease. by evaluation of haplotypes of associated family members; Tumor analyses have proven useful not only in narrowing in 100% of these cases, the wild-type allele was lost. In some the candidate region, thereby expediting the search for BRCAJ, of these families germline mutations in BRCA1 have been but have also provided data supporting the hypothesis that determined; analyses of tumors with LOH at BRCA1 have BRCAJ is a tumor suppressor gene (12, 13). Work from several laboratories (12-16) has revealed that sporadic and familial breast and ovarian tumors may exhibit the phenomenon of LOH Received 9/16/94; accepted 2/17/95. 1 Supported in part by NIH Grants GCRC-MCAP 3M01RR00042-34S1 (S. D. M.), ROl CA57601-01 (B. L. W.), and P30 HG00209 to the Genome Center at the University of Michigan. 3 The abbreviations used are: BRCAJ, breast cancer gene; LOH, loss of 2 To whom requests for reprints should be addressed, at Department of heterozygosity; CI, confidence interval; SSCP, single-strand conforma- Internal Medicine, 5510 MSRB I, University of Michigan Medical tion polymorphism; LOD score, base 10 logarithm of the odds favoring Center, Ann Arbor, MI 48109-0680. linkage. Downloaded from clincancerres.aacrjournals.org on September 28, 2021. © 1995 American Association for Cancer Research. 540 BRCAJ in Early Onset Breast and Ovarian Cancer in large and diverse ehnomosomal regions, including 17q21, neextraction of tumor/normal DNA from regions equivalent which supports the hypothesis that BRCAJ is likely to be a to those of the original extraction. It was then possible to tumor suppressor gene. In other words, functional loss of both apply uniform criteria for scoring LOH at all markers, even if BRCAJ alleles in the affected tissue(s) may be necessary for more than one extraction was necessary. malignant transformation to occur. In this model, affected mdi- PCR Amplification of Polymorphic Markers. PCR ne- viduals are presumed to be born with a genmline defect in the actions were performed on each tumor/normal pain, a normal BRCAJ gene, which constitutes the ‘ ‘first hit’ ‘ in Knudson’s human DNA control, and two on more samples from CEPH model for tumonigenesis by a tumor supressor gene. The second parents known to be informative for the marker being ana- defect is acquired somatically in the wild-type allele in the lyzed. DNA extraction reagents and water served as negative breast on ovarian tissue of these patients, thereby contributing to control template. The reaction volume was 35 jil. The neac- the development of cancer. One mechanism for disruption of the tion mixture consisted of 8 p.1 DNA template, 3.5 p.1 lOX Taq second allele can be an interstitial chromosomal deletion, de- polymenase buffer, 4.25 p.1 1.25 msi deoxynucleotide tniphos- teeted through loss of alleles at flanking polymorphic markers. phate mixture, 0.2 p.1 Taq polymenase, a variable amount of Thus, LOH is widely held to be an indicator of the presence of forward and reverse primer ranging from 0.8-1.5 jil of a 10 a tumor suppressor gene adjacent to the deleted markers. The ng/jil solution of each, and the remainder in double-distilled observations of LOH presented here support a tumor suppressor water. One of the primers was end labeled with [32P]dATP mechanism for BRCAJ. using T4 kinase. Annealing temperatures ranged between 53#{176}Cand 65#{176}C,depending on the primers, with an extension MATERIALS AND METHODS temperature of 72#{176}C.The annealing time was 1 mm whereas the extension time varied from 1 mm to 40 s + 5 s/cycle for Specimen Selection. Thirty-four paraffin-embedded breast 35 cycles. Optimization of conditions proceeded as follows: tumors from families likely to harbor BRCA1 germline mutations were obtained from the institutions where the patients had under- if amplification was not detected with an annealing temper- atune of 53#{176}C,the amount of template was increased to 12 p.1. gone surgical treatment, in accordance with guidelines from the University of Michigan Human Use Committee for the procure- Nonspecific signals were suppressed by increasing the an- nealing temperature and/or decreasing the primer concentra- ment of archival materials for research. Living family members tion. The PCR products were analyzed in 0.4-mm thick 8% provided informed consent to proceed with the analyses of their tumors; the results were not shared with the patients. All specimens denaturing polyacrylamide gels, which were subsequently dried and autonadiognaphed by standard techniques. underwent histological examination to confirm the diagnosis and to determine whether both neoplastie and normal components were Although it is widely acknowledged that the scoring of LOH is a qualitative assessment, we have used the following present. DNA Extraction. With the assistance of a surgical guidelines to ensure consistency of scoring. In experiments where the band intensity of the alleles varied between the pathologist (T. S. F.), each paraffin block was cut in 4-jim tumor and normal samples, but the wild-type allele was still sections and mounted on glass slides. Normal and neoplastic visible, the samples were neextracted from immediately tissue fractions were dissected with a single-use disposable razor blade under a dissecting microscope. This procedure adjacent sections at least two times and independent expeni- ments were performed on the tumor/normal pains. A de- minimized mixing of normal and tumor subpopulations, and crease in intensity of a band of oven 75% was required yielded tumor samples which were estimated to be at least for scoring LOH.
Load more

Recommended publications
  • Relaxed Selection in the Wild
    TREE-1109; No of Pages 10 Review Relaxed selection in the wild David C. Lahti1, Norman A. Johnson2, Beverly C. Ajie3, Sarah P. Otto4, Andrew P. Hendry5, Daniel T. Blumstein6, Richard G. Coss7, Kathleen Donohue8 and Susan A. Foster9 1 Department of Biology, University of Massachusetts, Amherst, MA 01003, USA 2 Department of Plant, Soil, and Insect Sciences, University of Massachusetts, Amherst, MA 01003, USA 3 Center for Population Biology, University of California, Davis, CA 95616, USA 4 Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada 5 Redpath Museum and Department of Biology, McGill University, Montreal, QC H3A 2K6, Canada 6 Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90095, USA 7 Department of Psychology, University of California, Davis, CA 95616, USA 8 Department of Biology, Duke University, Durham, NC 02138, USA 9 Department of Biology, Clark University, Worcester, MA 01610, USA Natural populations often experience the weakening or are often less clear than typical cases of trait evolution. removal of a source of selection that had been important When an environmental change results in strong selection in the maintenance of one or more traits. Here we refer to on a trait from a known source, a prediction for trait these situations as ‘relaxed selection,’ and review recent evolution often follows directly from this fact [2]. When studies that explore the effects of such changes on traits such a strong source of selection is removed, however, no in their ecological contexts. In a few systems, such as the clear prediction emerges. Rather, the likelihood of various loss of armor in stickleback, the genetic, developmental consequences can only be understood by integrating the and ecological bases of trait evolution are being discov- remaining sources of selection and processes at all levels of ered.
    [Show full text]
  • Inclusive Fitness As a Criterion for Improvement LSE Research Online URL for This Paper: Version: Accepted Version
    Inclusive fitness as a criterion for improvement LSE Research Online URL for this paper: http://eprints.lse.ac.uk/104110/ Version: Accepted Version Article: Birch, Jonathan (2019) Inclusive fitness as a criterion for improvement. Studies in History and Philosophy of Science Part C :Studies in History and Philosophy of Biological and Biomedical Sciences, 76. ISSN 1369-8486 https://doi.org/10.1016/j.shpsc.2019.101186 Reuse This article is distributed under the terms of the Creative Commons Attribution- NonCommercial-NoDerivs (CC BY-NC-ND) licence. This licence only allows you to download this work and share it with others as long as you credit the authors, but you can’t change the article in any way or use it commercially. More information and the full terms of the licence here: https://creativecommons.org/licenses/ [email protected] https://eprints.lse.ac.uk/ Inclusive Fitness as a Criterion for Improvement Jonathan Birch Department of Philosophy, Logic and Scientific Method, London School of Economics and Political Science, London, WC2A 2AE, United Kingdom. Email: [email protected] Webpage: http://personal.lse.ac.uk/birchj1 This article appears in a special issue of Studies in History & Philosophy of Biological & Biomedical Sciences on Optimality and Adaptation in Evolutionary Biology, edited by Nicola Bertoldi. 16 July 2019 1 Abstract: I distinguish two roles for a fitness concept in the context of explaining cumulative adaptive evolution: fitness as a predictor of gene frequency change, and fitness as a criterion for phenotypic improvement. Critics of inclusive fitness argue, correctly, that it is not an ideal fitness concept for the purpose of predicting gene- frequency change, since it relies on assumptions about the causal structure of social interaction that are unlikely to be exactly true in real populations, and that hold as approximations only given a specific type of weak selection.
    [Show full text]
  • Doxorubicin-Induced Death in Neuroblastoma Does Not Involve Death Receptors in S-Type Cells and Is Caspase-Independent in N-Type Cells
    Oncogene (2002) 21, 6132 – 6137 ª 2002 Nature Publishing Group All rights reserved 0950 – 9232/02 $25.00 www.nature.com/onc Doxorubicin-induced death in neuroblastoma does not involve death receptors in S-type cells and is caspase-independent in N-type cells Sally Hopkins-Donaldson1, Pu Yan1, Katia Balmas Bourloud1, Annick Muhlethaler1, Jean-Luc Bodmer2 and Nicole Gross*,1 1Department of Pediatric Onco-Hematology, Centre Hospitalier Universitaire Vaudois, CH1011 Lausanne, Switzerland; 2Institute of Biochemistry, University of Lausanne, CH-1066, Epalinges, Switzerland Death induced by doxorubicin (dox) in neuroblastoma tumors in infants frequently undergo spontaneous (NB) cells was originally thought to occur via the Fas remission. Failure to undergo programmed cell death pathway, however since studies suggest that caspase-8 is a putative mechanism for cancer cell resistance to expression is silenced in most high stage NB tumors, it is chemotherapy, while in contrast spontaneous remission more probable that dox-induced death occurs via a is thought to be a result of increased apoptosis (Oue et different mechanism. Caspase-8 silenced N-type invasive al., 1996). NB cell lines LAN-1 and IMR-32 were investigated for Apoptosis signaling occurs via two different path- their sensitivity to dox, and compared to S-type ways which converge on a common machinery of cell noninvasive SH-EP NB cells expressing caspase-8. All demise that is activated by caspases (Strasser et al., cell lines had similar sensitivities to dox, independently of 2000). The death receptor pathway is activated by caspase-8 expression. Dox induced caspase-3, -7, -8 and ligands of the tumor necrosis factor (TNF) family -9 and Bid cleavage in S-type cells and death was which induce the trimerization of their cognate blocked by caspase inhibitors but not by oxygen radical receptors (Daniel et al., 2001).
    [Show full text]
  • Genetically Modified Mosquitoes Educator Materials
    Genetically Modified Mosquitoes Scientists at Work Educator Materials OVERVIEW This document provides background information, discussion questions, and responses that complement the short video “Genetically Modified Mosquitoes” from the Scientists at Work series. The Scientists at Work series is intended to provide insights into the daily work of scientists that builds toward discoveries. The series focuses especially on scientists in the field and what motivates their work. This 8-minute 35-second video is appropriate for any life science student audience. It can be used as a review of the nature of science or to enhance a discussion on transgenic technology. Classroom implementation of the material in this document might include assigning select discussion questions to small groups of students or selecting the top five questions to discuss as a class. KEY CONCEPTS • Researchers genetically modified mosquitoes to help prevent the spread of a virus. • Male GM mosquitoes pass on a lethality gene to the offspring when they mate with non-GM females in the wild. CURRICULUM CONNECTIONS Standards Curriculum Connection NGSS (2013) HS-LS1.A, HS-LS3.A AP Bio (2015) 3.A.1 IB Bio (2016) 3.1, 3.5 Vision and Change (2009) CC1, CC2, CC3 PRIOR KNOWLEDGE Students should • be familiar with the idea that genes code for proteins and that genetic information can be passed to offspring. • have some understanding of transgenic technology and what it means for an organism to be genetically modified. BACKGROUND INFORMATION Mosquitoes can transmit pathogens that cause many human diseases, such as malaria, yellow fever, dengue fever, chikungunya, and Zika fever.
    [Show full text]
  • Transgenic Rescue from Embryonic Lethality and Renal Carcinogenesis in the Eker Rat Model by Introduction of a Wild-Type Tsc2 Ge
    Proc. Natl. Acad. Sci. USA Vol. 94, pp. 3990–3993, April 1997 Medical Sciences Transgenic rescue from embryonic lethality and renal carcinogenesis in the Eker rat model by introduction of a wild-type Tsc2 gene (hereditary cancerytwo-hit modelytumor suppressor geneyanimal modelygene therapy) TOSHIYUKI KOBAYASHI*, HIROAKI MITANI*, RI-ICHI TAKAHASHI†,MASUMI HIRABAYASHI†,MASATSUGU UEDA†, HIROSHI TAMURA‡, AND OKIO HINO*§ *Department of Experimental Pathology, Cancer Institute, 1-37-1 Kami-Ikebukuro, Toshima-ku, Tokyo 170, Japan; †YS New Technology Institute Inc., Shimotsuga-gun, Tochigi 329-05, Japan; and ‡Laboratory of Animal Center, Teikyo University School of Medicine, 2-11-1, Kaga, Itabashi-ku, Tokyo 173, Japan Communicated by Takashi Sugimura, National Cancer Center, Tokyo, Japan, February 3, 1997 (received for review December 9, 1996) ABSTRACT We recently reported that a germ-line inser- activity for Rap1a and localizes to Golgi apparatus. Other tion in the rat homologue of the human tuberous sclerosis gene potential functional domains include two transcriptional acti- (TSC2) gives rise to dominantly inherited cancer in the Eker vation domains (AD1 and AD2) in the carboxyl terminus of the rat model. In this study, we constructed transgenic Eker rats Tsc2 gene product (19), a zinc-finger-like region (our unpub- with introduction of a wild-type Tsc2 gene to ascertain lished observation), and a potential src-homology 3 region whether suppression of the Eker phenotype is possible. Rescue (SH3) binding domain (20). However, the function of tuberin from embryonic lethality of mutant homozygotes (EkeryEker) is not yet fully understood. and suppression of N-ethyl-N-nitrosourea-induced renal car- Human tuberous sclerosis is an autosomal dominant genetic cinogenesis in heterozygotes (Ekery1) were both observed, disease characterized by phacomatosis with manifestations defining the germ-line Tsc2 mutation in the Eker rat as that include mental retardation, seizures, and angiofibroma, embryonal lethal and tumor predisposing mutation.
    [Show full text]
  • I Xio- and Made the Rather Curious Assumption That the Mutant Is
    NOTES AND COMMENTS NATURAL SELECTION AND THE EVOLUTION OF DOMINANCE P. M. SHEPPARD Deportment of Genetics, University of Liverpool and E.B. FORD Genetic Laboratories, Department of Zoology, Oxford 1. INTRODUCTION CROSBY(i 963) criticises the hypothesis that dominance (or recessiveness) has evolved and is not an attribute of the allelomorph when it arose for the first time by mutation. None of his criticisms is new and all have been discussed many times. However, because of a number of apparent mis- understandings both in previous discussions and in Crosby's paper, and the fact that he does not refer to some important arguments opposed to his own view, it seems necessary to reiterate some of the previous discussion. Crosby's criticisms fall into two parts. Firstly, he maintains, as did Wright (1929a, b) and Haldane (1930), that the selective advantage of genes modifying dominance, being of the same order of magnitude as the mutation rate, is too small to have any evolutionary effect. Secondly, he criticises, as did Wright (5934), the basic assumption that a new mutation when it first arises produces a phenotype somewhat intermediate between those of the two homozygotes. 2.THE SELECTION COEFFICIENT INVOLVED IN THE EVOLUTION OF DOMINANCE Thereis no doubt that the selective advantage of modifiers of dominance is of the order of magnitude of the mutation rate of the gene being modified. Crosby (p. 38) considered a hypothetical example with a mutation rate of i xio-and made the rather curious assumption that the mutant is dominant in the absence of modifiers of dominance.
    [Show full text]
  • Using Drosophila to Teach Genetics
    Curriculum Units by Fellows of the Yale-New Haven Teachers Institute 1996 Volume V: Genetics in the 21st Century: Destiny, Chance or Choice Using Drosophila to Teach Genetics Curriculum Unit 96.05.01 by Christin E. Arnini The objectives of this unit are to take basic concepts of genetics and apply them to an organism, easily raised and observed in the classroom. It has been a challenge in the teaching of High School Biology, to take the abstract ideas of genes, chromosomes, heredity, and make them visable and tangible for the students. Drosophila melanogaster offers a way for teachers to help students make connections between populations, the organism, the cell, the chromosome, the gene, and the DNA. As a part of a unit on genetics, this unit on Drosophila can give students the opportunity to get to know an organism well, observing closely its development and physical characteristics, and then questioning how it is that the fly came to be this way. Unit Format: I. Discussion of Drosophila 1. Review of genetics concepts 2. Thomas Hunt Morgan and the historical frame 3. Drosophila chromosomes, characteristics, and developmental stages 4. Mutations 5. Homeobox genes 6. Homologs in other vertebrates 7. Making a map 8. DNA Sequencing II. Activities: 1. Observations of the individual flies, 2. Doing genetic crossses, and predicting offspring outcomes in the Lab, 3. Salivary gland extraction, and staining of chromosomes 4. Creating a genetic map 5. DNA sequencing simulation, 6. Virtual Fly Lab. III. Appendix IV. Bibliography and resources Curriculum Unit 96.05.01 1 of 21 Chromosomes are the structures that contain the hereditary material of an organism.
    [Show full text]
  • 1 the Limits of Selection Under Plant Domestication Robin G Allaby1
    The limits of selection under plant domestication Robin G Allaby1* ,Dorian Q Fuller2, James L Kitchen1, 3 1. School of Life Sciences, Gibbet Hill Campus, University of Warwick, Coventry CV4 7AL 2. Institute of Archaeology, University College London, 31-34 Gordon Square, London WC1H 0PY 3. Computational and Systems Biology, Rothamsted, Harpenden, Herts. * corresponding author email: [email protected] 1 Abstract Plant domestication involved a process of selection through human agency of a series of traits collectively termed the domestication syndrome. Current debate concerns the pace at which domesticated plants emerged from cultivated wild populations and how many genes were involved. Here we present simulations that test how many genes could have been involved by considering the cost of selection. We demonstrate the selection load that can be endured by populations increases with decreasing selection coefficients and greater numbers of loci down to values of about s = 0.005, causing a driving force that increases the number of loci under selection. As the number of loci under selection increases, an effect of co-selection increases resulting in individual unlinked loci being fixed more rapidly in out-crossing populations, representing a second driving force to increase the number of loci under selection. In inbreeding systems co-selection results in interference and reduced rates of fixation but does not reduce the size of the selection load that can be endured. These driving forces result in an optimum pace of genome evolution in which 50-100 loci are the most that could be under selection in a cultivation regime. Furthermore, the simulations do not preclude the existence of selective sweeps but demonstrate that they come at a cost of the selection load that can be endured and consequently a reduction of the capacity of plants to adapt to new environments, which may contribute to the explanation of why selective sweeps have been so rarely detected in genome studies.
    [Show full text]
  • How Genetic Engineering Differs from Conventional Breeding Hybridization
    GENETIC ENGINEERING IS NOT AN EXTENSION OF CONVENTIONAL PLANT BREEDING; How genetic engineering differs from conventional breeding, hybridization, wide crosses and horizontal gene transfer by Michael K. Hansen, Ph.D. Research Associate Consumer Policy Institute/Consumers Union January, 2000 Genetic engineering is not just an extension of conventional breeding. In fact, it differs profoundly. As a general rule, conventional breeding develops new plant varieties by the process of selection, and seeks to achieve expression of genetic material which is already present within a species. (There are exceptions, which include species hybridization, wide crosses and horizontal gene transfer, but they are limited, and do not change the overall conclusion, as discussed later.) Conventional breeding employs processes that occur in nature, such as sexual and asexual reproduction. The product of conventional breeding emphasizes certain characteristics. However these characteristics are not new for the species. The characteristics have been present for millenia within the genetic potential of the species. Genetic engineering works primarily through insertion of genetic material, although gene insertion must also be followed up by selection. This insertion process does not occur in nature. A gene “gun”, a bacterial “truck” or a chemical or electrical treatment inserts the genetic material into the host plant cell and then, with the help of genetic elements in the construct, this genetic material inserts itself into the chromosomes of the host plant. Engineers must also insert a “promoter” gene from a virus as part of the package, to make the inserted gene express itself. This process alone, involving a gene gun or a comparable technique, and a promoter, is profoundly different from conventional breeding, even if the primary goal is only to insert genetic material from the same species.
    [Show full text]
  • Basic Molecular Genetics for Epidemiologists F Calafell, N Malats
    398 GLOSSARY Basic molecular genetics for epidemiologists F Calafell, N Malats ............................................................................................................................. J Epidemiol Community Health 2003;57:398–400 This is the first of a series of three glossaries on CHROMOSOME molecular genetics. This article focuses on basic Linear or (in bacteria and organelles) circular DNA molecule that constitutes the basic physical molecular terms. block of heredity. Chromosomes in diploid organ- .......................................................................... isms such as humans come in pairs; each member of a pair is inherited from one of the parents. general increase in the number of epide- Humans carry 23 pairs of chromosomes (22 pairs miological research articles that apply basic of autosomes and two sex chromosomes); chromo- science methods in their studies, resulting somes are distinguished by their length (from 48 A to 257 million base pairs) and by their banding in what is known as both molecular and genetic epidemiology, is evident. Actually, genetics has pattern when stained with appropriate methods. come into the epidemiological scene with plenty Homologous chromosome of new sophisticated concepts and methodologi- cal issues. Each of the chromosomes in a pair with respect to This fact led the editors of the journal to offer the other. Homologous chromosomes carry the you a glossary of terms commonly used in papers same set of genes, and recombine with each other applying genetic methods to health problems to during meiosis. facilitate your “walking” around the journal Sex chromosome issues and enjoying the articles while learning. Sex determining chromosome. In humans, as in Obviously, the topics are so extensive and inno- all other mammals, embryos carrying XX sex vative that a single short glossary would not be chromosomes develop as females, whereas XY sufficient to provide you with the minimum embryos develop as males.
    [Show full text]
  • Antiviral Rnai in Insects and Mammals: Parallels and Differences
    viruses Review Antiviral RNAi in Insects and Mammals: Parallels and Differences Susan Schuster, Pascal Miesen and Ronald P. van Rij * Department of Medical Microbiology, Radboud University Medical Center, Radboud Institute for Molecular Life Sciences, 6500 HB Nijmegen, The Netherlands; [email protected] (S.S.); [email protected] (P.M.) * Correspondence: [email protected]; Tel.: +31-24-3617574 Received: 16 April 2019; Accepted: 15 May 2019; Published: 16 May 2019 Abstract: The RNA interference (RNAi) pathway is a potent antiviral defense mechanism in plants and invertebrates, in response to which viruses evolved suppressors of RNAi. In mammals, the first line of defense is mediated by the type I interferon system (IFN); however, the degree to which RNAi contributes to antiviral defense is still not completely understood. Recent work suggests that antiviral RNAi is active in undifferentiated stem cells and that antiviral RNAi can be uncovered in differentiated cells in which the IFN system is inactive or in infections with viruses lacking putative viral suppressors of RNAi. In this review, we describe the mechanism of RNAi and its antiviral functions in insects and mammals. We draw parallels and highlight differences between (antiviral) RNAi in these classes of animals and discuss open questions for future research. Keywords: small interfering RNA; RNA interference; RNA virus; antiviral defense; innate immunity; interferon; stem cells 1. Introduction RNA interference (RNAi) or RNA silencing was first described in the model organism Caenorhabditis elegans [1] and following this ground-breaking discovery, studies in the field of small, noncoding RNAs have advanced tremendously. RNAi acts, with variations, in all eukaryotes ranging from unicellular organisms to complex species from the plant and animal kingdoms [2].
    [Show full text]
  • Suppression Mechanisms Reviews Suppression Mechanisms Themes from Variations
    Suppression mechanisms Reviews Suppression mechanisms themes from variations Suppressor analysis is a commonly used strategy to identify functional relationships between genes that might not have been revealed through other genetic or biochemical means. Many mechanisms that explain the phenomenon of genetic suppression have been described, but the wide variety of possible mechanisms can present a challenge to defining the relationship between a suppressor and the original gene. This article provides a broad framework for classifying suppression mechanisms and describes a series of genetic tests that can be applied to determine the most likely mechanism of suppression. he analysis of any biological process by classical genetic basis for distinguishing the classes, allowing the investigator Tmethods ultimately requires multiple types of mutant to: (1) pursue the class that best suits their particular interests; selections to identify all the genes involved in that process. (2) identify systematically the relationship between the two One strategy commonly used to identify functionally gene products; and (3) design rationally future suppressor related genes is to begin with a strain that already contains hunts to increase the likelihood of obtaining the desired a mutation affecting the pathway of interest, selecting for classes of mutations. Some practical aspects should be mutations that modify its phenotype. Modifiers that result considered when designing suppressor hunts (Box 1). in a more severe phenotype are termed enhancers, while mutations that restore a more wild-type phenotype despite Intragenic suppression the continued presence of the original mutation are termed The simplest suppression mechanism to conceptualize is suppressors. Historically, suppressors have proven intragenic suppression, where a phenotype caused by a extremely valuable for determining the relationship primary mutation is ameliorated by a second mutation in between two gene products in vivo, even in the absence of the same gene.
    [Show full text]