{"id":768,"date":"2026-06-08T02:29:14","date_gmt":"2026-06-08T06:29:14","guid":{"rendered":""},"modified":"2026-06-08T02:29:14","modified_gmt":"2026-06-08T06:29:14","slug":"dna-repair-ii","status":"publish","type":"post","link":"https:\/\/c2creset.ondigit.us\/?p=768","title":{"rendered":"DNA Repair II"},"content":{"rendered":"<p style=\"text-align: center;\"><span style=\"color: rgb(0, 102, 153);\"><strong><span style=\"font-size: small;\"><span style=\"font-family: Verdana;\">DNA Repair II<\/span><\/span><\/strong><\/span><\/p>\n<p style=\"text-align: center;\"><span style=\"color: rgb(0, 102, 153);\"><strong><span style=\"font-size: small;\"><span style=\"font-family: Verdana;\">DNA Mis-Match Repair (MMR)<br \/>\n<\/span><\/span><\/strong><\/span><\/p>\n<p style=\"text-align: center;\"><iframe loading=\"lazy\" height=\"160\" frameborder=\"0\" width=\"260\" src=\"http:\/\/www.youtube.com\/embed\/ESBL6Qxsi90\" allowfullscreen=\"\"><\/iframe><\/p>\n<p style=\"text-align: left;\"><span style=\"font-size: small;\"><span style=\"font-family: Verdana;\">The DNA Mis-Match Repair (MMR) pathway has evolved to correct errors made by DNA polymerase during DNA replication. Such errors fall into two broad categories: <br \/>\n<\/span><\/span><\/p>\n<ol>\n<li><span style=\"font-size: small;\"><span style=\"font-family: Verdana;\">base substitutions, and <\/span><\/span><\/li>\n<li><span style=\"font-size: small;\"><span style=\"font-family: Verdana;\">insertions\/deletions.<\/span><\/span><\/li>\n<\/ol>\n<p><span style=\"font-size: small;\"><span style=\"font-family: Verdana;\">1.\tA base substitution error occurs when DNA polymerase inserts an incorrect  nucleotide opposite the template base, like a T opposite G instead of C, or A opposite C instead of G. <\/span><\/span><\/p>\n<p><span style=\"font-size: small;\"><span style=\"font-family: Verdana;\">These incorrect base pairs are referred to as mismatches. Often, DNA polymerase will make an error when copying a base that has been distorted by <a href=\"?p=766\"><span style=\"color: rgb(0, 0, 255);\">alkylation<\/span><\/a>, such as inserting a T opposite O6-methyl-Guanine on the other strand.<\/span><\/span><\/p>\n<p style=\"text-align: center;\"><iframe loading=\"lazy\" height=\"170\" frameborder=\"0\" width=\"260\" src=\"http:\/\/www.youtube.com\/embed\/HYS6EKnQcv0\" allowfullscreen=\"\"><\/iframe><\/p>\n<p><span style=\"font-size: small;\"><span style=\"font-family: Verdana;\">2.\tAn insertion error occurs when DNA polymerase adds several extra nucleotides to a sequence; a deletion error is made when several nucleotides are omitted from a sequence. Sequences that contain repeats of the same nucleotide such as AAAAAA, are very vulnerable to insertion\/deletion errors.<\/span><\/span><\/p>\n<p><span style=\"font-size: small;\"><span style=\"font-family: Verdana;\">Other repetitive sequences, like the di-nucleotide repeat CACACACA and the tri-nucleotide repeat CTGCTGCTG, are prone to insertion\/deletion errors as well. These ones are called micro-satellites.<\/span><\/span><\/p>\n<p><span style=\"font-size: small;\"><span style=\"font-family: Verdana;\">Defects in DNA mismatch repair have been found in different types of cancer. Micro-satellite sequences that are shorter or longer than normal are typical of defective MMR. <\/span><\/span><\/p>\n<p><span style=\"font-size: small;\"><span style=\"font-family: Verdana;\">Expansion of tri-nucleotide repeat sequences is associated with various hereditary neurological disorders, such as myotonic dystrophy and Huntington&#8217;s disease.<\/span><\/span><\/p>\n<p><span style=\"font-size: small;\"><span style=\"font-family: Verdana;\">The process of MMR is like the BER and NER pathways:<br \/>\n<\/span><\/span><\/p>\n<ol>\n<li><span style=\"font-size: small;\"><span style=\"font-family: Verdana;\">a mismatch must be recognized by a group of proteins that specialize in that particular type of distortion, <\/span><\/span><\/li>\n<li><span style=\"font-size: small;\"><span style=\"font-family: Verdana;\">a phosphodiester bond in the DNA strand containing the mismatched nucleotide is cleaved, then displaced by DNA helicase, and that section is then removed,<br \/>\n    <\/span><\/span><\/li>\n<li><span style=\"font-size: small;\"><span style=\"font-family: Verdana;\">DNA polymerase carries out the DNA repair synthesis, <\/span><\/span><\/li>\n<li><span style=\"font-size: small;\"><span style=\"font-family: Verdana;\">DNA ligase restores the sugar-phosphate backbone. <\/span><\/span><\/li>\n<\/ol>\n<p><span style=\"font-size: small;\"><span style=\"font-family: Verdana;\">The patch of DNA newly synthesized by the MMR DNA polymerase is about 1,000 nucleotides long, compared to BER, which typically replaces 1 nucleotide, or NER, which replaces about 30 nucleotides. <\/span><\/span><\/p>\n<p><span style=\"font-size: small;\"><span style=\"font-family: Verdana;\">MMR is especially important in tissues that are constantly regenerating, like the lining of the uterus and the intestines.<\/span><\/span><\/p>\n<p style=\"text-align: center;\"><span style=\"font-size: small;\"><span style=\"font-family: Verdana;\"><img loading=\"lazy\" decoding=\"async\" src=\"\/userfiles\/image\/2014%20pics\/CRISPR.jpg\" width=\"222\" height=\"140\" alt=\"\" \/><br \/>\n<\/span><\/span><\/p>\n<p><span style=\"font-size: small;\"><span style=\"font-family: Verdana;\">Certain bacterial cells can identify invading viruses and chop up their DNA. CRISPR-Cas9 adapts that technique to allow us to edit genes nad remove harmful diseases.<\/span><\/span><\/p>\n<p><span style=\"font-family: Verdana; font-size: small;\">Cas9 is a modified protein injected into a body to work on the DNA, like scissors that can snip the genes.<\/span><\/p>\n<p style=\"text-align: right;\"><a href=\"?p=629\"><span style=\"font-size: x-small;\"><span style=\"font-family: Verdana;\"><strong><span style=\"color: rgb(0, 0, 255);\">read more &#8230;<\/span><\/strong><\/span><\/span><\/a><\/p>\n<p style=\"text-align: right;\">&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>DNA Repair II DNA Mis-Match Repair (MMR) The DNA Mis-Match Repair (MMR) pathway has evolved to correct errors made by DNA polymerase during DNA replication. Such errors fall into two broad categories: base substitutions, and insertions\/deletions. 1. A base substitution error occurs when DNA polymerase inserts an incorrect nucleotide opposite the template base, like a&#8230;<\/p>\n","protected":false},"author":1,"featured_media":1769,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_kad_post_transparent":"","_kad_post_title":"","_kad_post_layout":"","_kad_post_sidebar_id":"","_kad_post_content_style":"","_kad_post_vertical_padding":"","_kad_post_feature":"","_kad_post_feature_position":"","_kad_post_header":false,"_kad_post_footer":false,"_kad_post_classname":"","footnotes":""},"categories":[],"tags":[],"class_list":["post-768","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry"],"_links":{"self":[{"href":"https:\/\/c2creset.ondigit.us\/index.php?rest_route=\/wp\/v2\/posts\/768","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/c2creset.ondigit.us\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/c2creset.ondigit.us\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/c2creset.ondigit.us\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/c2creset.ondigit.us\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=768"}],"version-history":[{"count":0,"href":"https:\/\/c2creset.ondigit.us\/index.php?rest_route=\/wp\/v2\/posts\/768\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/c2creset.ondigit.us\/index.php?rest_route=\/wp\/v2\/media\/1769"}],"wp:attachment":[{"href":"https:\/\/c2creset.ondigit.us\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=768"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c2creset.ondigit.us\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=768"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/c2creset.ondigit.us\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=768"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}