Date of download: 5/31/2016 From: The Hereditary Nonpolyposis Colorectal Cancer Syndrome: Genetics and Clinical Implications[dhelix] Ann Intern Med. 2003;138(7): doi: / Events at the replication fork.After primers anneal to the individual strands, synthesis of new complementary DNA proceeds in a 5′ to 3′ direction. This occurs on both strands and at both replication forks. Therefore, replication proceeds bi-directionally. Synthesis of DNA is continuous along the leading strand but discontinuous along the lagging strand because of opposing directions of movement of the replication fork and DNA elongation. A, B, and C represent sequential time points. Figure Legend: Copyright © American College of Physicians. All rights reserved.American College of Physicians

Date of download: 5/31/2016 From: The Hereditary Nonpolyposis Colorectal Cancer Syndrome: Genetics and Clinical Implications[dhelix] Ann Intern Med. 2003;138(7): doi: / Slippage during DNA replication.MSSMSIThe DNA polymerase enzyme adds complementary deoxynucleotide bases to the growing strand. Slippage may occur when microsatellite DNA sequences are encountered. In this example, there are six copies of a CA dinucleotide repeat. Because of slippage, an additional CA repeat is inserted, resulting in a mismatched loop of DNA. With an intact DNA mismatch repair system, the error is corrected and DNA microsatellite stability ( ) is observed. However, when the DNA mismatch repair system is mutated, the error is not corrected and microsatellite instability ( ) results. Figure Legend: Copyright © American College of Physicians. All rights reserved.American College of Physicians

Date of download: 5/31/2016 From: The Hereditary Nonpolyposis Colorectal Cancer Syndrome: Genetics and Clinical Implications[dhelix] Ann Intern Med. 2003;138(7): doi: / Components of the DNA mismatch repair system.The DNA mismatch repair system can correct either single base-pair mismatches or larger loops of mismatched DNA. hMSH2 serves as the “scout” that recognizes mismatched DNA. It forms a complex with either hMSH6 or hMSH3, depending on the number of mismatched nucleotides. A second heterodimeric complex (hMLH1/hPMS1) is then recruited to excise the mispaired nucleotides. hMutSα = hMSH2/hMSH6; hMutSβ = hMSH2/hMSH3; hMutLα = hMLH1/hPMS1. bp = base pair. Figure Legend: Copyright © American College of Physicians. All rights reserved.American College of Physicians

Date of download: 5/31/2016 From: The Hereditary Nonpolyposis Colorectal Cancer Syndrome: Genetics and Clinical Implications[dhelix] Ann Intern Med. 2003;138(7): doi: / The conversion technique.MSH2MSH2Human blood mononuclear cells are fused with mouse cells. Several outcomes are possible. Often, one of the two human chromosomes is lost in the fused heterokaryon. These can be identified through the use of polymorphic markers for a specific chromosome. These specific populations are then amplified, and their DNA is analyzed for mutations in a specific DNA mismatch repair gene. In this manner, only one allele is analyzed at a time. = wild type; * = mutant. Figure Legend: Copyright © American College of Physicians. All rights reserved.American College of Physicians

Date of download: 5/31/2016 From: The Hereditary Nonpolyposis Colorectal Cancer Syndrome: Genetics and Clinical Implications[dhelix] Ann Intern Med. 2003;138(7): doi: / Overall strategy for genetic testing of an affected proband from a suspected hereditary nonpolyposis colorectal cancer kindred.MSIIHCasterisk†If the Amsterdam criteria are fulfilled, then genetic testing of an affected family member should proceed. Consideration can also be given to directly testing persons who fulfill Bethesda criteria 1 through 3. At-risk relatives should be tested only after a pathogenic mutation is identified within the family. Persons with negative results on microsatellite instability ( ) or immunohistochemistry ( ) testing still require clinical cancer screening as dictated by their personal and family medical histories ( ). Inconclusive results are defined as no mutation or missense mutation ( ). MSI-H = high level of MSI (MSI-H phenotype); MSI-L = low level of MSI (MSI-L phenotype); MSS = microsatellite stable. Figure Legend: Copyright © American College of Physicians. All rights reserved.American College of Physicians

Date of download: 5/31/2016 From: The Hereditary Nonpolyposis Colorectal Cancer Syndrome: Genetics and Clinical Implications[dhelix] Ann Intern Med. 2003;138(7): doi: / Immunohistochemical staining for MSH2 and MLH1 protein.ACDFA.B.C.D.E.F.Representative images using specific antiserum for MSH2 protein (Calbiochem, La Jolla, California) and MLH1 protein (Pharmingen, San Diego, California) in two cases of colon cancer from individuals with the hereditary nonpolyposis colorectal cancer syndrome demonstrating loss of MLH1 staining in case 1 ( – ) and loss of MSH2 staining in case 2 ( – ). Positive staining for MLH1 in a normal colon. Absent staining for MLH1 in a cancerous colon. Positive staining for MSH2 in a cancerous colon. Positive staining for MSH2 in a normal colon. Positive staining for MLH1 in a cancerous colon. Absent staining for MSH2 in colon cancer. Bar = 100 µm. Slides provided by Jonathan Terdiman, with permission. Figure Legend: Copyright © American College of Physicians. All rights reserved.American College of Physicians