DOCSLIB.ORG

How to Conquer a Chromosome Abnormality

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
How to Conquer a Chromosome Abnormality How to Conquer a Chromosome Abnormality— What is a chromosome abnormality? University of Texas Health Science Center at San Antonio, School of Medicine The Chromosome 18 Registry and Research Society What is a chromosome 18 abnormality? Special points of interest: When confronted with a chromosome foods to how susceptible you are to Genetic material—genes, abnormality diagnosis, parents often infections. These units of instruction chromosomes, DNA have an avalanche of questions; the within your body are essentially the Chromosome anatomy first of which is “What is a chromo- cookbook of life. The individual units some abnormality?” In order to under- are called genes. Genes are organized Chromosome analysis stand what a chromosome abnormali- within cells into packages called chro- Common chromosome 18 ty is, we first need to understand what mosomes much like recipes are orga- syndromes a chromosome is and some back- nized in chapters in cookbooks. ground about genetics. You may have heard of the human You have surely noticed that children genome. Think of this as the cookbook tend to look like their parents, often of life. It contains all the recipes you having some features like their mom will ever need. And every cell in the and some like their dad. This is be- body contains the complete cookbook cause they received half of their ge- with all the recipes. As the cookbook netic material from each parent. is divided into chapters, our genome is Inside this issue: divided into chromosomes. And as Your genetic material contains the each chapter has many recipes, each instructions for every part of your Chromosome Analysis 2 chromosome contains many genes. Genome = Cookbook body. These instructions are for virtu- While the cookbook is made of paper, Chromosomes = Chapters ally everything from how your ears your genes and chromosomes are Genes = Recipes 18q- 2 are shaped to how you digest your made of DNA. 18p- 2 Chromosome anatomy—important to understand Ring 18 3 The top picture is of chromosomes The bottom picture shows the chromosomes paired up and in numerical order. This makes from a white blood cell viewed under a 3 Tetrasomy 18p light microscope. They have been analysis easier. Chromosomes are found in treated with stain that makes them pairs, one from mom and one from dad. Males have one X and one Y chromosome while Trisomy 18 3 appear to have black and white bands. However, this random assortment of females have two X chromosomes. Each chromosome has a “waistband” called a cen- 4 chromosomes is difficult to analyze Summary tromere, and two arms—the short arm is the for differences from normal. p arm and the long arm is the q arm. How to Conquer a Chromosome Abnormality—What is a chromosome abnormality? Page 2 Chromosome Analysis The analysis of chromo- changes are not compatible chromsomes. somes involves looking for with life. The majority of Because chromosomes are missing pieces, duplicated babies conceived who have made up of genetic material pieces, rearrangements chromosome changes are (genes) the results can cause or losses or gains of entire miscarried early in preg- abnormal development or func- chromosomes. Quite liter- nancy. Babies with any type tion. ally, anything you could do of chromosome changes to a piece of paper with that survive are said to have scissors, glue and a copy chromosome abnormalities. machine, could really hap- So, a chromosome abnor- pen and does really happen mality is a change in the to chromosomes. However, content or structure of the majority of these “A chromosome The Most Common Syndromes of Chromosome 18 abnormality is a 18q- change in the This picture shows 18q-, a deletion middle of the long arm and as such content or of any portion of the long arm, also would be called an interstitial dele- structure of called the q arm. Someone could tion. It is also important to appre- chromosomes.” have a deletion that is smaller or ciate that one chromosome is 18q- larger than the one pictured. The normal and only one chromosome deletion could be from the end of of the pair has the deletion the chromosome like in the picture and thus would be called a termi- nal deletion. The deletion could also be from somewhere in the 18p- Shown here is 18p-. Like 18q-, the 18p deletions can be large or small, terminal or interstitial. 18p- 18p– involves the short or p arm of one of the two copies of chromosome 18. How to Conquer a Chromosome Abnormality—What is a chromosome abnormality? Page 3 Ring 18 Shown here is Ring 18. In this chromosome can be large or condition one of the two chro- small. There could be a big q mosomes forms a ring. This arm deletion and a small p arm means that by definition, the deletion or two small deletions protective cap called the telo- or any combination. It is im- mere is missing from each end portant to note that the deletion of the chromosome. However of genes in ring chromosomes Ring 18 that does not mean that genes always involves the ends of the must be missing from both ends chromosome arms. of the chromosome—but they usually are. Again like the other two conditions, the size of the deletion from either end of the “Because Tetrasomy 18p chromosomes are Shown to the left is Tetra- chromosome 18 p arm, made up of genetic somy 18p. In this condition which is why it is called material (genes), there are two normal copies Tetrasomy 18p. the results can of chromosome 18 along with an extra chromosome com- Tetrasomy 18p cause abnormal posed of two p arms of chro- development or mosome 18. This means there function.” are a total of 4 copies of the Trisomy 18 The last major syndrome of children with Trisomy 18 usu- chromosome 18 is Trisomy 18, ally have shortened lifespans in which there are simply 3 and many die before their copies of chromosome 18. first birthday. Trisomy 18 This is, by far, the most com- mon of the chromosome 18 syndromes. However, this condition is different from the other conditions because UTHSCSA—Department of Pediatrics The Chromosome 18 Clinical Research Center For more information, you may contact the authors and principal investigators of the Chromosome 18 Clinical MSC 7820 Research Center at the phone numbers or email shown to the left. 7703 Floyd Curl Drive San Antonio, TX 78229-3900 Authors & Principal Investigators: Phone: 210-567-5321 Fax: 210-567-0919 Jannine D. Cody, PhD and Daniel E. Hale, MD E-mail: [email protected] Our Motto To provide individuals and families affected by chromosome 18 abnormalities with comprehensive medical and educational information with a focus on treatment options. We are on the web! http://pediatrics.uthscsa.edu/centers/chromosome18/ Summary To summarize, this is what you have learned so far: Your genetic material is pack- aged in chromosomes. The chromosomes contain genes. Information provided by The Chromosome 18 Clinical Genes are the instructions for Research Center to: all body development and func- tion. There is a variety of chromo- some copy number changes that can occur. When they do occur, normal development and function is often altered. http://www.chromosome18.org/ 210-657-4968 .
Load more

Recommended publications
  • Chromosome 18
    Chromosome 18 Description Humans normally have 46 chromosomes in each cell, divided into 23 pairs. Two copies of chromosome 18, one copy inherited from each parent, form one of the pairs. Chromosome 18 spans about 78 million DNA building blocks (base pairs) and represents approximately 2.5 percent of the total DNA in cells. Identifying genes on each chromosome is an active area of genetic research. Because researchers use different approaches to predict the number of genes on each chromosome, the estimated number of genes varies. Chromosome 18 likely contains 200 to 300 genes that provide instructions for making proteins. These proteins perform a variety of different roles in the body. Health Conditions Related to Chromosomal Changes The following chromosomal conditions are associated with changes in the structure or number of copies of chromosome 18. Distal 18q deletion syndrome Distal 18q deletion syndrome occurs when a piece of the long (q) arm of chromosome 18 is missing. The term "distal" means that the missing piece (deletion) occurs near one end of the chromosome arm. The signs and symptoms of distal 18q deletion syndrome include delayed development and learning disabilities, short stature, weak muscle tone ( hypotonia), foot abnormalities, and a wide variety of other features. The deletion that causes distal 18q deletion syndrome can occur anywhere between a region called 18q21 and the end of the chromosome. The size of the deletion varies among affected individuals. The signs and symptoms of distal 18q deletion syndrome are thought to be related to the loss of multiple genes from this part of the long arm of chromosome 18.
    [Show full text]
  • 22Q13.3 Deletion Syndrome
    22q13.3 deletion syndrome Description 22q13.3 deletion syndrome, which is also known as Phelan-McDermid syndrome, is a disorder caused by the loss of a small piece of chromosome 22. The deletion occurs near the end of the chromosome at a location designated q13.3. The features of 22q13.3 deletion syndrome vary widely and involve many parts of the body. Characteristic signs and symptoms include developmental delay, moderate to profound intellectual disability, decreased muscle tone (hypotonia), and absent or delayed speech. Some people with this condition have autism or autistic-like behavior that affects communication and social interaction, such as poor eye contact, sensitivity to touch, and aggressive behaviors. They may also chew on non-food items such as clothing. Less frequently, people with this condition have seizures or lose skills they had already acquired (developmental regression). Individuals with 22q13.3 deletion syndrome tend to have a decreased sensitivity to pain. Many also have a reduced ability to sweat, which can lead to a greater risk of overheating and dehydration. Some people with this condition have episodes of frequent vomiting and nausea (cyclic vomiting) and backflow of stomach acids into the esophagus (gastroesophageal reflux). People with 22q13.3 deletion syndrome typically have distinctive facial features, including a long, narrow head; prominent ears; a pointed chin; droopy eyelids (ptosis); and deep-set eyes. Other physical features seen with this condition include large and fleshy hands and/or feet, a fusion of the second and third toes (syndactyly), and small or abnormal toenails. Some affected individuals have rapid (accelerated) growth.
    [Show full text]
  • Chromosome Abberrations N Genetic Diseases
    Chromosomal Analysis Dr. Monisha Banerjee Professor Molecular & Human Genetics Laboratory Department of Zoology University of Lucknow Lucknow-226007 Chromosome Morphology Telomere Short arm (p) Centromere Arm Long arm (q) Telomere Metacentric Submetacentric Acrocentric Defining Chromosomal Location Arm Region Band Subband 3 2 2 1 2 2 p 1 1 5 1 4 1 3 2 1 1 2 17 q 1 1 . 2 1 1 3 1 2 2 q 3 1 3 2, 3 4 2 1 4 2 Chromosome 17 3 Nomenclature system Visualizing Metaphase Chromosomes • Patient cells are incubated and divide in tissue culture. • Phytohemagglutinin (PHA): stimulates cell division. • Colcemid: arrests cells in metaphase. • 3:1 Methanol:Acetic Acid: fixes metaphase chromosomes for staining. Visualizing Metaphase Chromosomes (Banding) • Giemsa-, reverse- or centromere-stained metaphase chromosomes G-Bands R-Bands C-Bands Karyotype • International System for Human Cytogenetic Nomenclature (ISCN) – 46, XX – normal female – 46, XY – normal male • G-banded chromosomes are identified by band pattern. Normal Female Karyotype (46, XX) (G Banding) Types of Chromosomal Aberrations Numerical Abnormalities Structural Abnormalities Aneuploidy Aneuploidy occurs when one of the chromosomes is present in an abnormal number of copies. Trisomy and monosomy are two forms of aneuploidy. Chromosome Number Abnormality Aneuploidy (48, XXXX) Chromosome Number Abnormality Trisomy 21 (47, XX, +21) Down Syndrome is Caused by Trisomy for Chromosome 21 Aneuploidy is remarkably common, causing termination of at least 25% of human conceptions. Aneuploidy is also a driving force in cancer progression (virtually all cancer cells are aneuploid). Chromosome Non-Disjunction in Meiosis Causes Aneuploidy The Frequency of Chromosome Non-Disjunction And Down Syndrome Rises Sharply with Maternal Age Chromosome Number Abnormality Trisomy 13 (47, XX, +13) Trisomy 18 (47, XY,+18) Sex Chromosome Aneuploid Conditions are Common Klinefelter syndrome Polyploidy Polyploidy occurs when all the chromosomes are present in three or more copies.
    [Show full text]
  • Dr. Fern Tsien, Dept. of Genetics, LSUHSC, NO, LA Down Syndrome
    COMMON TYPES OF CHROMOSOME ABNORMALITIES Dr. Fern Tsien, Dept. of Genetics, LSUHSC, NO, LA A. Trisomy: instead of having the normal two copies of each chromosome, an individual has three of a particular chromosome. Which chromosome is trisomic determines the type and severity of the disorder. Down syndrome or Trisomy 21, is the most common trisomy, occurring in 1 per 800 births (about 3,400) a year in the United States. It is one of the most common genetic birth defects. According to the National Down Syndrome Society, there are more than 400,000 individuals with Down syndrome in the United States. Patients with Down syndrome have three copies of their 21 chromosomes instead of the normal two. The major clinical features of Down syndrome patients include low muscle tone, small stature, an upward slant to the eyes, a single deep crease across the center of the palm, mental retardation, and physical abnormalities, including heart and intestinal defects, and increased risk of leukemia. Every person with Down syndrome is a unique individual and may possess these characteristics to different degrees. Down syndrome patients Karyotype of a male patient with trisomy 21 What are the causes of Down syndrome? • 95% of all Down syndrome patients have a trisomy due to nondisjunction before fertilization • 1-2% have a mosaic karyotype due to nondisjunction after fertilization • 3-4% are due to a translocation 1. Nondisjunction refers to the failure of chromosomes to separate during cell division in the formation of the egg, sperm, or the fetus, causing an abnormal number of chromosomes. As a result, the baby may have an extra chromosome (trisomy).
    [Show full text]
  • The Epidemiology of Sex Chromosome Abnormalities
    Received: 12 March 2020 Revised: 11 May 2020 Accepted: 11 May 2020 DOI: 10.1002/ajmg.c.31805 RESEARCH REVIEW The epidemiology of sex chromosome abnormalities Agnethe Berglund1,2,3 | Kirstine Stochholm3 | Claus Højbjerg Gravholt2,3 1Department of Clinical Genetics, Aarhus University Hospital, Aarhus, Denmark Abstract 2Department of Molecular Medicine, Aarhus Sex chromosome abnormalities (SCAs) are characterized by gain or loss of entire sex University Hospital, Aarhus, Denmark chromosomes or parts of sex chromosomes with the best-known syndromes being 3Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Turner syndrome, Klinefelter syndrome, 47,XXX syndrome, and 47,XYY syndrome. Denmark Since these syndromes were first described more than 60 years ago, several papers Correspondence have reported on diseases and health related problems, neurocognitive deficits, and Agnethe Berglund, Department of Clinical social challenges among affected persons. However, the generally increased comor- Genetics, Aarhus University Hospital, Aarhus, Denmark. bidity burden with specific comorbidity patterns within and across syndromes as well Email: [email protected] as early death of affected persons was not recognized until the last couple of Funding information decades, where population-based epidemiological studies were undertaken. More- Familien Hede Nielsens Fond; Novo Nordisk over, these epidemiological studies provided knowledge of an association between Fonden, Grant/Award Numbers: NNF13OC0003234, NNF15OC0016474 SCAs and a negatively reduced socioeconomic status in terms of education, income, retirement, cohabitation with a partner and parenthood. This review is on the aspects of epidemiology in Turner, Klinefelter, 47,XXX and 47,XYY syndrome. KEYWORDS 47,XXX syndrome, 47,XYY syndrome, epidemiology, Klinefelter syndrome, Turner syndrome 1 | INTRODUCTION 100 participants, and many with much fewer participants.
    [Show full text]
  • Maternal Age, History of Miscarriage, and Embryonic/Fetal Size Are Associated with Cytogenetic Results of Spontaneous Early Miscarriages
    Journal of Assisted Reproduction and Genetics (2019) 36:749–757 https://doi.org/10.1007/s10815-019-01415-y GENETICS Maternal age, history of miscarriage, and embryonic/fetal size are associated with cytogenetic results of spontaneous early miscarriages Nobuaki Ozawa1 & Kohei Ogawa1 & Aiko Sasaki1 & Mari Mitsui1 & Seiji Wada1 & Haruhiko Sago1 Received: 1 October 2018 /Accepted: 28 January 2019 /Published online: 9 February 2019 # Springer Science+Business Media, LLC, part of Springer Nature 2019 Abstract Purpose To clarify the associations of the maternal age, history of miscarriage, and embryonic/fetal size at miscarriage with the frequencies and profiles of cytogenetic abnormalities detected in spontaneous early miscarriages. Methods Miscarriages before 12 weeks of gestation, whose karyotypes were evaluated by G-banding between May 1, 2005, and May 31, 2017, were included in this study. The relationships between their karyotypes and clinical findings were assessed using trend or chi-square/Fisher’s exact tests and multivariate logistic analyses. Results Three hundred of 364 miscarriage specimens (82.4%) had abnormal karyotypes. An older maternal age was significantly associated with the frequency of abnormal karyotype (ptrend < 0.001), particularly autosomal non-viable and viable trisomies (ptrend 0.001 and 0.025, respectively). Women with ≥ 2 previous miscarriages had a significantly lower possibility of miscarriages with abnormal karyotype than women with < 2 previous miscarriages (adjusted odds ratio [aOR], 0.48; 95% confidence interval [95% CI], 0.27–0.85). Although viable trisomy was observed more frequently in proportion to the increase in embryonic/fetal size at miscarriage (ptrend < 0.001), non-viable trisomy was observed more frequently in miscarriages with an embryonic/fetal size < 10 mm (aOR, 2.41; 95% CI, 1.27–4.58), but less frequently in miscarriages with an embryonic/fetal size ≥ 20 mm (aOR, 0.01; 95% CI, 0.00–0.07) than in anembryonic miscarriages.
    [Show full text]
  • Chromosomal Abnormalities Worksheet Answer Key
    Chromosomal Abnormalities Worksheet Answer Key Smitten or unpurposed, Jodie never exudate any conjoiner! Jeremiah bifurcated her examinees unchangeably, she buss it bedward. Emery tip haughtily. If a gene usually appear shortly after the chromosomal abnormalities worksheet answer key concepts, or structure of being used the foundation for the two different MEIOSIS and Gametogenesis TASK CARDS with licence Key. You dispatch wish to depart the differences between pedigree analysis and gene sequencing and have students think about when open use each method. There first many inherited disorders in the efficacy population. The abnormality found in individuals, abnormalities can happen after reading and significant amounts of. An abnormal number abnormalities worksheet answer key concepts as they answered each case western philosophy has also will prevent students worksheets is. Ne if intake of chromosomes Questions 1 What is the purpose with a conducting a karyotype anal 2 What causes a dark countryside on a chromosome veomans. Possessing three copies of four particular chromosome instead bend the normal two copies. In research institute of abnormalities worksheet answer key distinguishing feature of any other healthcare professional. After students complete the discussion, of DNA and RNA. Answers to cut out a normal humans with giemsa dye that is also many adolescents and answers i, discontinuous boundaries between malignancy and! We have vision issues often cannot see if a chromosome abnormality showing an individual is an advantage? 142 Human Genetic Disorders Worksheet Answers. A simple to understand how by Chromosome 2 years ago 7 minutes 3 seconds 3734 views What crime a chromosome abnormality disorder anomaly. Pak 6 study guide answerspdf Parkway Schools.
    [Show full text]
  • The Cytogenetics of Hematologic Neoplasms 1 5
    The Cytogenetics of Hematologic Neoplasms 1 5 Aurelia Meloni-Ehrig that errors during cell division were the basis for neoplastic Introduction growth was most likely the determining factor that inspired early researchers to take a better look at the genetics of the The knowledge that cancer is a malignant form of uncon- cell itself. Thus, the need to have cell preparations good trolled growth has existed for over a century. Several biologi- enough to be able to understand the mechanism of cell cal, chemical, and physical agents have been implicated in division became of critical importance. cancer causation. However, the mechanisms responsible for About 50 years after Boveri’s chromosome theory, the this uninhibited proliferation, following the initial insult(s), fi rst manuscripts on the chromosome makeup in normal are still object of intense investigation. human cells and in genetic disorders started to appear, fol- The fi rst documented studies of cancer were performed lowed by those describing chromosome changes in neoplas- over a century ago on domestic animals. At that time, the tic cells. A milestone of this investigation occurred in 1960 lack of both theoretical and technological knowledge with the publication of the fi rst article by Nowell and impaired the formulations of conclusions about cancer, other Hungerford on the association of chronic myelogenous leu- than the visible presence of new growth, thus the term neo- kemia with a small size chromosome, known today as the plasm (from the Greek neo = new and plasma = growth). In Philadelphia (Ph) chromosome, to honor the city where it the early 1900s, the fundamental role of chromosomes in was discovered (see also Chap.
    [Show full text]
  • The Origin and Impact of Embryonic Aneuploidy
    Hum Genet DOI 10.1007/s00439-013-1309-0 ORIGINAL INVESTIGATION The origin and impact of embryonic aneuploidy Elpida Fragouli • Samer Alfarawati • Katharina Spath • Souraya Jaroudi • Jonas Sarasa • Maria Enciso • Dagan Wells Received: 15 March 2013 / Accepted: 11 April 2013 Ó Springer-Verlag Berlin Heidelberg 2013 Abstract Despite the clinical importance of aneuploidy, divisions. All abnormalities appeared to be tolerated until surprisingly little is known concerning its impact during activation of the embryonic genome, after which some the earliest stages of human development. This study aimed forms started to decline in frequency. However, many an- to shed light on the genesis, progression, and survival of euploidies continued to have little impact, with affected different types of chromosome anomaly from the fertilized embryos successfully reaching the blastocyst stage. Results oocyte through the final stage of preimplantation devel- from the direct analyses of female meiotic divisions and opment (blastocyst). 2,204 oocytes and embryos were early embryonic stages suggest that chromosome errors examined using comprehensive cytogenetic methodology. present during preimplantation development have origins A diverse array of chromosome abnormalities was detec- that are more varied than those seen in later pregnancy, ted, including many forms never recorded later in devel- raising the intriguing possibility that the source of aneu- opment. Advancing female age was associated with ploidy might modulate impact on embryo viability. The dramatic increase in aneuploidy rate and complex chro- results of this study also narrow the window of time for mosomal abnormalities. Anaphase lag and congression selection against aneuploid embryos, indicating that most failure were found to be important malsegregation causing survive until the blastocyst stage and, since they are not mechanisms in oogenesis and during the first few mitotic detected in clinical pregnancies, must be lost around the time of implantation or shortly thereafter.
    [Show full text]
  • Guide to Aneuploidy Screening Options
    On behalf of BIDMC Prenatal Genetics and Maternal-Fetal Medicine BIDMC Prenatal Genetics Guide to Aneuploidy Screening Options While most pregnancies are healthy, there is a small chance in any pregnancy for there to be a genetic condition or birth defect. A chromosome abnormality is one type of genetic condition. This type of condition is not usually inherited, but can happen for the first time in any fetus, just by chance. A chromosome is a package of genes or instructions. We have 46 chromosomes in each of our cells, 23 that come from the egg and 23 that come from the sperm. When an egg or sperm has an extra or missing chromosome the resulting fetus is said to have a chromosome abnormality. The most common chromosome abnormality is Down syndrome (extra chromosome #21). Some chromosome abnormalities are more severe and some are less severe than Down syndrome. Chromosome abnormalities happen more often as the pregnant patient gets older. Your provider can tell you the chance for a chromosome abnormality in your pregnancy based on your age, and will also offer you “screening tests.” These are non-invasive tests that can better predict the chance for a fetus to have a chromosomal abnormality. These tests are entirely optional. Also available are invasive tests, like amniocentesis, that can tell for sure if a fetus has a chromosome abnormality and can detect a wider range of more rare chromosome abnormalities, but pose a small risk for miscarriage. The decision about which test to have performed, if any, can be difficult and confusing.
    [Show full text]
  • Cryptic Subtelomeric Translocation T(2;16)(Q37;Q24) Segregating in a Family with Unexplained Stillbirths and a Dysmorphic, Slightly Retarded Child
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by AIR Universita degli studi di Milano European Journal of Human Genetics (2001) 9, 881 ± 886 ã 2001 Nature Publishing Group All rights reserved 1018-4813/01 $15.00 www.nature.com/ejhg ARTICLE Cryptic subtelomeric translocation t(2;16)(q37;q24) segregating in a family with unexplained stillbirths and a dysmorphic, slightly retarded child Daniela Giardino*,1, Palma Finelli1, Giulietta Gottardi1, Donata Clerici2, Fabio Mosca2, Vincenza Briscioli3 and Lidia Larizza1,4 1Laboratorio di Citogenetica, Istituto Auxologico Italiano, Milan, Italy; 2Dipartimento di Neonatologia, ICP, Milan, Italy; 3Dipartimento di Medicina di Laboratorio, Settore Specialistico Genetica Medica, ICP, Milan, Italy; 4Dipartimento di Biologia e Genetica, UniversitaÁ degliStudi,Milan,Italy We here describe a submicroscopic translocation affecting the subtelomeric regions of chromosomes 2q and 16q, and segregating in a family with stillbirths, early pregnancy losses, and two dysmorphic and slightly retarded babies. FISH analysis showed a 46,XY,der(2)t(2;16)(q37.3;q24.3) in the propositus, and a balanced t(2;16) in his mother, her conceptus and maternal grandfather. FISH with YACs and BACs made it possible to map the 2q37 breakpoint precisely between the regions covered by y952E1 and y746H1, and the 16q breakpoint between the regions encompassed by bA 309g16 and bA 533d19. The contribution of 2q37.3 monosomy and 16q24.3 trisomy to the proband's phenotype is compared with that in reported patients with similar imbalances of either chromosome. European Journal of Human Genetics (2001) 9, 881 ± 886.
    [Show full text]
  • Chromosome Abnormalities
    Testing for Chromosome Abnormalities Department of Obstetrics and Gynecology Maternal-Fetal Medicine and Prenatal Genetics Congratulations on your pregnancy! While most babies are born healthy, approximately 3-5% will be affected with certain birth defects or genetic conditions. In all pregnancies, tests are offered that can tell if the pregnancy may be at high risk for a condition called a chromosome abnormality. Decisions about testing in pregnancy are personal. Some choose not to have any testing done. Others find the information from testing to be helpful. We have made this booklet to give some information on the tests available. We hope that having this information and discussing it with your OB/GYN provider will help you to decide whether this testing makes sense for you and your family. What are chromosomes? Our bodies are made of tiny cells. Chromosomes are the packages of genetic information (DNA) inside our Chromosome cells. They contain the instructions for our growth Cell and development. Usually, each person has a total of 46 chromosomes in each cell. The chromosomes come in pairs (23 pairs). Each parent contributes one chromosome to each pair. When a fetus (developing baby) has extra or missing chromosomes, it can lead to medical problems. An extra chromosome (three copies instead of two) is called a trisomy. A missing chromosome (one copy instead of two) is called a monosomy. This type of genetic condition doesn’t usually run in families. It can happen just by chance in any pregnancy. DNA What are the most common chromosomal abnormalities? The most common differences related to the number of chromosomes are: • Down syndrome: Down syndrome is also called trisomy 21.
    [Show full text]