{"id":1403,"date":"2020-08-06T23:15:38","date_gmt":"2020-08-06T23:15:38","guid":{"rendered":"https:\/\/meddists.com\/learn\/pre-clinical\/medical-genetics\/cytogenetics\/cytogenetic-methods\/"},"modified":"2021-01-31T22:12:50","modified_gmt":"2021-01-31T21:12:50","slug":"cytogenetic-methods","status":"publish","type":"page","link":"https:\/\/meddists.com\/learn\/pre-clinical\/medical-genetics\/cytogenetics\/cytogenetic-methods\/","title":{"rendered":"Cytogenetic Methods"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\"><div class=\"intro\">Cytogenetic methods are techniques used to study and observe the structure and behavior of chromosomes.<\/div><\/p>\n\n\n\n<hr class=\"wp-block-separator\"\/>\n\n\n<span class=\"block-heading\" id=\"header_1\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Basics of Cytogenetic Methods<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_1\">\n\n\n<p class=\"wp-block-paragraph\">We can use cytogenetic methods to detect and verify numerical or structural abnormalities in chromosomes during pre or postnatal screenings and oncology. These involve <strong>Giemsa staining<\/strong>, <strong>banding<\/strong>, and <strong>long time cell culture<\/strong> for metaphase cells.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For smaller aberrations, we use molecular cytogenetic methods such as Fluorescence In Situ Hybridization (FISH) and Comparative Genomic Hybridization (CGH).<\/p>\n\n\n<\/span><span class=\"block-heading\" id=\"header_2\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Fluorescence In Situ Hybridization (FISH)<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_2\">\n\n\n<p class=\"wp-block-paragraph\">FISH involves the use of fluorescence dye and microscope to visualize either a stretch of DNA or the DNA as a whole. The steps are shown below;<\/p>\n\n\n\n<ol class=\"wp-block-list\"><li>The target DNA to be visualized is isolated from the nucleus and is denatured to separate the two strands<\/li><li>The probe DNA( this DNA sequence has already been sequenced in the lab) is taken and is labelled with a fluorophore (fluorescent molecules)<\/li><li>The probe DNA is denatured<\/li><li>The target and probe DNA are mixed. Due to complementary base pairing, the DNA probe sequence will hybridize with its complementary sequence on the target DNA( which is the DNA region that we want to view)<\/li><li>The region of target DNA that we want to view ( which has now hybridized with the labelled probe DNA) can be viewed under a fluorescence microscope and checked for numerical and \/or structural aberrations.<\/li><\/ol>\n\n\n\n<p class=\"wp-block-paragraph\">The DNA probes can be<strong> centromere-specific<\/strong> (for viewing the centromeric region of DNA), locus-specific (for viewing a particular region or stretch of DNA) or <strong>whole chromosome-specific<\/strong> (for viewing the whole chromosome e.g during karyotyping).<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">FISH is good for detecting both balanced and unbalanced chromosomal aberrations.<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><a href=\"https:\/\/meddists.com\/wp-content\/uploads\/2020\/01\/640px-PLoSBiol3.5.Fig7ChromosomesAluFish.jpg\" target=\"_blank\" title=\"Cytogenetic Methods\"><img decoding=\"async\" src=\"https:\/\/meddists.com\/wp-content\/uploads\/2020\/01\/640px-PLoSBiol3.5.Fig7ChromosomesAluFish-600x164.jpg\" alt=\"\" class=\"wp-image-23336\"\/><\/a><figcaption><strong>Visualization of a normal female karyotype; 46, XX using Fluorescence In Situ Hybridization<\/strong> (Credit: Andreas Bolzer, Gregor Kreth, Irina Solovei, Daniela Koehler, Kaan Saracoglu, Christine Fauth, Stefan M\u00fcller, Roland Eils, Christoph Cremer, Michael R. Speicher, Thomas Cremer, CC BY 2.5)<\/figcaption><\/figure><\/div>\n\n\n<\/span><span class=\"block-heading\" id=\"header_3\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Comparative Genomic Hybridization (CGH)<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_3\">\n\n\n<p class=\"wp-block-paragraph\">As its name suggests, CGH is used to compare 2 DNA strands; one being the probe DNA and the other being the target DNA. The steps are shown below<\/p>\n\n\n\n<ol class=\"wp-block-list\"><li>The target DNA and the probe DNA isolated and both are labeled with fluorophores (fluorescent molecules) of different colors (usually red and green).<\/li><li>Next, the DNA strands are denatured to single-stranded DNA<\/li><li>The single-stranded target DNA and probe DNA are hybridized to a metaphase spread of chromosomes, to which the labeled DNA samples will bind at their locus of origin.<\/li><li>Using a fluorescence microscope and computer software, the differentially colored fluorescent signals are then compared along the length of each chromosome for the identification of chromosomal differences between the two sources. A higher intensity of the test sample color in a specific region of a chromosome indicates the gain of the material of that region in that corresponding region, while a higher intensity of the reference sample color indicates the loss of material in the test sample in that specific region. A neutral color (yellow when the fluorophore labels are red and green) indicates no difference between the two samples in that location.<\/li><\/ol>\n\n\n\n<p class=\"wp-block-paragraph\">CGH is only able to detect unbalanced chromosomal abnormalities. This is because balanced chromosomal abnormalities such as reciprocal translocation, inversions or ring chromosomes affect copy number, which is what is detected by the CGH method.<\/p>\n<\/span><div id=\"the_titles\" style=\"display:none;\"><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Basics of Cytogenetic Methods<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Fluorescence In Situ Hybridization (FISH)<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Comparative Genomic Hybridization (CGH)<\/h4><\/div>","protected":false},"excerpt":{"rendered":"<p>Basics of Cytogenetic Methods We can use cytogenetic methods to detect and verify numerical or structural abnormalities in chromosomes during pre or postnatal screenings and oncology. These involve Giemsa staining, banding, and long time cell culture for metaphase cells. For smaller aberrations, we use molecular cytogenetic methods such as Fluorescence In Situ Hybridization (FISH) and [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":1354,"menu_order":2,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-1403","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>Cytogenetic Methods &#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\/cytogenetic-methods\/\" \/>\n<meta name=\"twitter:label1\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data1\" content=\"3 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\\\/cytogenetic-methods\\\/\",\"url\":\"https:\\\/\\\/meddists.com\\\/learn\\\/pre-clinical\\\/medical-genetics\\\/cytogenetics\\\/cytogenetic-methods\\\/\",\"name\":\"Cytogenetic Methods &#8211; 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