{"id":1401,"date":"2020-08-06T23:15:08","date_gmt":"2020-08-06T23:15:08","guid":{"rendered":"https:\/\/meddists.com\/learn\/pre-clinical\/medical-genetics\/cytogenetics\/chromosomal-aberrations\/"},"modified":"2021-02-06T12:13:14","modified_gmt":"2021-02-06T11:13:14","slug":"chromosomal-aberrations","status":"publish","type":"page","link":"https:\/\/meddists.com\/learn\/pre-clinical\/medical-genetics\/cytogenetics\/chromosomal-aberrations\/","title":{"rendered":"Chromosomal Aberrations"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\"><div class=\"intro\">A <strong>chromosomal aberration<\/strong> (or mutation) occurs when any defect occurs to chromosomes or part of them.<\/div><\/p>\n\n\n<span class=\"block-heading\" id=\"header_1\">\n<h2 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Types of Chromosomal Aberrations<\/h2>\n<\/span><span class=\"block-content\" id=\"contents_1\">\n\n\n<p class=\"wp-block-paragraph\">There are two types of chromosomal aberrations<\/p>\n\n\n\n<ol class=\"wp-block-list\"><li>Numerical Aberrations<\/li><li>Structural Aberrations<\/li><\/ol>\n\n\n<\/span><span class=\"block-heading\" id=\"header_2\">\n<h3 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title2\">Numerical aberrations<\/h3>\n<\/span><span class=\"block-content\" id=\"contents_2\">\n\n\n<p class=\"wp-block-paragraph\"><b>A<\/b>bnormalities that involve a change in the number of chromosomes but not in the structural or physical appearance of the chromosomes. Numerical aberrations are caused by nondisjunction (failure of homologous chromosomes or sister chromatids to separate properly during cell division) either during meiosis I, meiosis II OR mitosis.<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><a href=\"https:\/\/meddists.com\/wp-content\/uploads\/2020\/01\/Nondisjunction_in_Mitosis.jpg\" target=\"_blank\" title=\"Chromosomal Aberrations\"><img decoding=\"async\" src=\"https:\/\/meddists.com\/wp-content\/uploads\/2020\/01\/Nondisjunction_in_Mitosis.jpg\" alt=\"\" class=\"wp-image-23355\"\/><\/a><figcaption><strong>Non-disjunction in Mitosis<\/strong> (Credit; Alex Federspiel, CC BY-SA 4.0)<\/figcaption><\/figure><\/div>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><a href=\"https:\/\/meddists.com\/wp-content\/uploads\/2020\/01\/download.png\" target=\"_blank\" title=\"Chromosomal Aberrations\"><img decoding=\"async\" src=\"https:\/\/meddists.com\/wp-content\/uploads\/2020\/01\/download.png\" alt=\"\" class=\"wp-image-23356\"\/><\/a><figcaption><strong>Non-disjunction in Meiosis II( for the first picture) and Meiosis I(for the second picture)<\/strong>. (Credit; Tweety207,CC BY-SA 3.0)<\/figcaption><\/figure><\/div>\n\n\n\n<p class=\"wp-block-paragraph\">Numerical aberrations can be euploidy or aneuploidy.<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li><strong>Euploidy: <\/strong>is the state of a cell or organism having more than one set of chromosomes. The normal chromosomal numbers are diploid(2n) for somatic cells and haploid(n) for germ cells. Any extra sets e.g 3n, 4n, etc are called euploidy and they are not compatible with life. Any euploid embryo will be spontaneously aborted in the uterus.<\/li><li><strong>Aneuploidy:&nbsp;<\/strong> is the state of a cell or organism having more or less than 46 chromosomes but not as much as a whole set i.e euploidy. Aneuploidy can be monosomy; 45 chromosomes, trisomy; 47 chromosomes, tetrasomy; 48 chromosomes, etc. Some important mentions for aneuploidy are listed below<\/li><\/ul>\n\n\n<\/span><span class=\"block-heading\" id=\"header_3\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title3\">Examples<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_3\">\n\n\n<ul class=\"wp-block-list\"><li><strong>Turner Syndrome:<\/strong> 45, X. This is an example of monosomy because there is only one copy of the X chromosomes. This is the only monosomy that is compatible with life. The others will be spontaneously aborted in utero. No Barr bodies will be present in this organism. The women present with short stature and non-functioning ovaries which causes infertility and some of them may also have extra skin on the neck (webbed neck).<\/li><li><strong>Triple X syndrome:<\/strong><ul><li>The karyotype is 47, XXX. <\/li><li>This is an example of trisomy because there are three copies of the X chromosome. <\/li><li>There are 2 Barr bodies present in the organism. <\/li><li>Normal feminine phenotype.<\/li><\/ul><\/li><li><strong>Klinefelter syndrome<\/strong><ul><li>The karyotype is 47, XXY. <\/li><li>This is an example of trisomy because there are three copies of the sex chromosomes. <\/li><li>There is only one Barr body present in the organism. <\/li><li>The patients have gynecomasty and outer genitals are reduced. They have a male phenotype.<\/li><\/ul><\/li><li><strong>X chromosome tetrasomy<\/strong><ul><li>The karyotype is 48, XXXX. <\/li><li>This is an example of tetrasomy because there are four copies of the X chromosome. <\/li><li>There are 3 Barr bodies present in the organism. <\/li><li>Presents with mental retardation.<\/li><\/ul><\/li><li><strong>X chromosome pentasomy<\/strong><ul><li>The karyotype is 49, XXXXX. <\/li><li>This is an example of pentasomy because there are five copies of the X chromosome. <\/li><li>There are 4 Barr bodies present in the organism. <\/li><li>Presents with mental retardation.<\/li><\/ul><\/li><li><strong>Down&#8217;s syndrome<\/strong><ul><li>The karyotype is 47,XX +21 or 47, XY +21. <\/li><li>It is caused by an extra copy of Chromosome 21 (trisomy 21) which can be due to non-disjunction or a Robertsonian translocation <em>(discussed in detail in the Cytogenetics: Chromosomal aberrations\u00a0lesson)<\/em>. <\/li><li>Presents with physical growth delays, mild to moderate intellectual disability, and characteristic facial features such as a small chin, slanted eyes, a flat nasal bridge, and a protruding tongue due to a small mouth.<\/li><\/ul><\/li><li><strong>Edwards syndrome<\/strong><ul><li>The karyotype is 47,XX +18 or 47, XY +18. <\/li><\/ul><ul><li>It is caused by an extra copy of Chromosome 18 (trisomy 18). <\/li><li>General symptoms involve kidney malformations, structural heart defects at birth, intestines protruding outside the body (omphalocele), developmental delays, growth deficiency, developmental delays, growth deficiency, small head accompanied by a prominent back portion of the head, low-set, malformed ears, abnormally small jaw, and a cleft lip\/palate.<\/li><\/ul><\/li><li><strong>Patau&#8217;s syndrome<\/strong><ul><li>The karyotype if 47,XX +13 or 47, XY +13. <\/li><li>It is caused by an extra copy of Chromosome 13 (trisomy 13) which can be due to non-disjunction or a Robertsonian translocation <em>(discussed in detail in the Cytogenetics: Chromosomal aberrations\u00a0lesson)<\/em>. <\/li><li>Presents with intellectual disability and motor disorder, kidney defects, cleft palate, abnormal genitalia, and polydactyl.<\/li><\/ul><\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">The risk of these numerical aberrations are greatly influenced by maternal age (for women over35, the risk is much higher).<\/p>\n\n\n<\/span><span class=\"block-heading\" id=\"header_4\">\n<h3 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title2\">Structural aberrations<\/h3>\n<\/span><span class=\"block-content\" id=\"contents_4\">\n\n\n<p class=\"wp-block-paragraph\">Abnormalities that result from breakage and incorrect rejoining of chromosomal segments. They can be isochromosome, deletions, duplications, balanced and unbalanced translocations, inversions and ring formation.<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><a href=\"https:\/\/meddists.com\/wp-content\/uploads\/2020\/01\/Isochromosome.gif\" target=\"_blank\" title=\"Chromosomal Aberrations\"><img decoding=\"async\" src=\"https:\/\/meddists.com\/wp-content\/uploads\/2020\/01\/Isochromosome.gif\" alt=\"\" class=\"wp-image-23270\"\/><\/a><figcaption><strong>Diagram of Isochromosome; Structural aberrations.<\/strong><br>(Credit: Kazulanth)<\/figcaption><\/figure><\/div>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><a href=\"https:\/\/meddists.com\/wp-content\/uploads\/2020\/01\/Types-of-mutation-1.png\" target=\"_blank\" title=\"Chromosomal Aberrations\"><img decoding=\"async\" src=\"https:\/\/meddists.com\/wp-content\/uploads\/2020\/01\/Types-of-mutation-1.png\" alt=\"\" class=\"wp-image-23360\"\/><\/a><figcaption><strong>Types of Chromosomal structural abberations<\/strong><\/figcaption><\/figure><\/div>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><a href=\"https:\/\/meddists.com\/wp-content\/uploads\/2020\/01\/Ring_chromosome.gif\" target=\"_blank\" title=\"Chromosomal Aberrations\"><img decoding=\"async\" src=\"https:\/\/meddists.com\/wp-content\/uploads\/2020\/01\/Ring_chromosome.gif\" alt=\"\" class=\"wp-image-23363\"\/><\/a><figcaption><strong>Diagram of ring chromosome; Structural aberrations.<\/strong> ( Credit; Kazulanth)<\/figcaption><\/figure><\/div>\n\n\n<\/span><span class=\"block-heading\" id=\"header_5\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title3\">Examples<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_5\">\n\n\n<ul class=\"wp-block-list\"><li><strong>Philadelphia Chromosome:<\/strong> This chromosome is formed due to reciprocal translocation of genetic material between chromosomes 9 and 22, and contains a fusion gene called <i>BCR-ABL<\/i>. This fusion gene codes for a hybrid protein: a tyrosine kinase protein that is &#8220;always-on&#8221;, causing the cell to divide uncontrollably by interrupting the stability of the genome and impairing various signalling pathways governing the cell cycle. It is seen in the cells of CML (Chronic Myeloid Leukemia)<\/li><li><strong>Cri du Chat syndrome:&nbsp;<\/strong>this is caused by a deletion on Chromosome 5. Affected children have a characteristic &#8216;cat-like&#8217; cry due to issues with the larynx and nervous system. Other symptoms include feeding problems, poor growth, severe cognitive, speech and motor disabilities and behavioural problems such as hyperactivity, aggression, outbursts and repetitive movements.&nbsp;<\/li><li><strong><strong>Robertsonian translocation:&nbsp;<\/strong><\/strong>this is a type of translocation involving two homologous or non-homologous chromosomes and is when they both break at their centromeres (centromeres are specialized DNA sequence of a chromosome that links a pair of sister chromatids and the long arms fuse to form a single, large chromosome with a single centromere. It occurs in the five acrocentric chromosome pairs (chromosome pairs where the short arms are fairly short), namely 13, 14, 15, 21 and 22.<\/li><\/ul>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><a href=\"https:\/\/meddists.com\/wp-content\/uploads\/2020\/01\/544px-Schematic_of_the_Philadelphia_Chromosome.svg_.png\" target=\"_blank\" title=\"Chromosomal Aberrations\"><img decoding=\"async\" src=\"https:\/\/meddists.com\/wp-content\/uploads\/2020\/01\/544px-Schematic_of_the_Philadelphia_Chromosome.svg_.png\" alt=\"\" class=\"wp-image-23369\"\/><\/a><figcaption><strong>Philadelphia Chromosome<\/strong> (Credit; Aryn89, CC BY-SA 4.0)<\/figcaption><\/figure><\/div>\n<\/span><div id=\"the_titles\" style=\"display:none;\"><h2 class=\"wp-block-heading\" class=\"wp-block-heading\">Types of Chromosomal Aberrations<\/h2><h3 class=\"wp-block-heading\" class=\"wp-block-heading\">Numerical aberrations<\/h3><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Examples<\/h4><h3 class=\"wp-block-heading\" class=\"wp-block-heading\">Structural aberrations<\/h3><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Examples<\/h4><\/div>","protected":false},"excerpt":{"rendered":"<p>Types of Chromosomal Aberrations There are two types of chromosomal aberrations Numerical Aberrations Structural Aberrations Numerical aberrations Abnormalities that involve a change in the number of chromosomes but not in the structural or physical appearance of the chromosomes. Numerical aberrations are caused by nondisjunction (failure of homologous chromosomes or sister chromatids to separate properly during [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":1354,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-1401","page","type-page","status-publish","hentry"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.8 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Chromosomal Aberrations &#8211; Meddists<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/meddists.com\/learn\/pre-clinical\/medical-genetics\/cytogenetics\/chromosomal-aberrations\/\" \/>\n<meta name=\"twitter:label1\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data1\" content=\"6 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/meddists.com\\\/learn\\\/pre-clinical\\\/medical-genetics\\\/cytogenetics\\\/chromosomal-aberrations\\\/\",\"url\":\"https:\\\/\\\/meddists.com\\\/learn\\\/pre-clinical\\\/medical-genetics\\\/cytogenetics\\\/chromosomal-aberrations\\\/\",\"name\":\"Chromosomal Aberrations &#8211; 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