Southern blot analysis of the X-linked red-green gene locus Southern blot analysis of the X-linked red-green gene locus. (A) Partial restriction maps of the red and green pigment genes. E, EcoRl; B, BamHl; R, Rsal. Open boxes denote the six exons. The restriction fragments A–D used in distinguishing red from green-specific sequences are shown below the genes. The A–C fragments derived from the red opsin gene (Ar, Br, Cr) are longer than those derived from the green gene (Ag, Bg, Cg) due to a 1.5-kb insertion in the first intron (wavy line). The absence of a Rsal site in the green opsin exon 5 accounts for the larger Rsal fragment of the green opsin gene (Dg). (Adapted with permission from Nathans et al.11 ) (B) Autoradiograph of Southern blots of genomic DNA samples from males with normal and defective color vision digested with either a combination of EcoRl and BamHl or Rsal. The EcoRl-BamHl fragments (B and C) were detected by hybridization to a 350-bp cDNA probe encompassing exon 1 and part of exon 2, whereas the D fragments were detected by a 400-bp genomic probe from the 3′ end of intron 4 of the green opsin gene.11 Typical examples of Southern blot patterns were selected. Lane 1: An individual with protanopia who has a single red-green hybrid gene with the C and D fragments of the red gene replaced by the corresponding fragments of the green pigment gene. Lane 2: A deuteranomalous individual who has normal red pigment gene and a green-red hybrid pigment gene (see diagram in part C). Lane 3: An individual with deuteranopia who has only a normal red gene (see diagram in part C). Lane 4: A deuteranomalous individual with a gene array comprised of normal red and green as well as a green red hybrid pigment genes. Lane 5: An individual with normal color vision who has multiple green pigment genes. The unmarked lanes show patterns similar to those described above. (C) Diagrammatic representation of Southern blot patterns for males with normal and defective color vision. The color vision phenotypes and the structure of the red-green gene arrays associated with the EcoRl-BamHl, and Rsal Southern blot patterns are shown above the Southern blot. Filled and open arrows denote red and green gene sequences, respectively. The width of the solid lines representing restriction fragments reflects the relative quantity of DNA that is quantified by densitometry. In protanomaly and protanopia (protan), the Dr fragment is missing, indicating loss of the 3′ portion of the red pigment gene, while the 5′ portion of the green gene is present. In deuteranopia, Bg, Cg, and Dg fragments are missing, indicating complete deletion of the green pigment gene. In deuteranomaly, the relative proportions of fragments is shifted, indicating the presence of green-red hybrid genes. Source: Color Vision and Its Genetic Defects, The Online Metabolic and Molecular Bases of Inherited Disease Citation: Valle D, Beaudet AL, Vogelstein B, Kinzler KW, Antonarakis SE, Ballabio A, Gibson K, Mitchell G. The Online Metabolic and Molecular Bases of Inherited Disease; 2014 Available at: https://ommbid.mhmedical.com/DownloadImage.aspx?image=/data/books/971/ch238fg9.png&sec=62662464&BookID=971&ChapterSecID=62662391&imagename=&gboscontainerID=0 Accessed: October 18, 2017 Copyright © 2017 McGraw-Hill Education. All rights reserved