diff --git a/packages/ove/cypress/e2e/unit/getStructuredBases.spec.js b/packages/ove/cypress/e2e/unit/getStructuredBases.spec.js
new file mode 100644
index 00000000..da69bbbf
--- /dev/null
+++ b/packages/ove/cypress/e2e/unit/getStructuredBases.spec.js
@@ -0,0 +1,192 @@
+import { getStructuredBases } from "../../../src/RowItem/StackedAnnotations/getStructuredBases";
+
+describe("getStructuredBases", () => {
+  it("works for fully-overlapping non origin-spanning case", () => {
+    const fullSequence = "ACGTCCACGT";
+    let primerSeq = "ACGT";
+    const start = 0;
+    const end = 3;
+    let { allBasesWithMetaData } = getStructuredBases({
+      annotationRange: { start, end },
+      forward: true,
+      bases: primerSeq,
+      start: start,
+      end: end,
+      fullSequence,
+      primerBindsOn: "3prime",
+      sequenceLength: fullSequence.length
+    });
+
+    let expected = [true, true, true, true];
+    assert.deepEqual(
+      allBasesWithMetaData.map(({ isMatch }) => isMatch),
+      expected
+    );
+
+    primerSeq = "CCGT";
+    ({ allBasesWithMetaData } = getStructuredBases({
+      annotationRange: { start, end },
+      forward: true,
+      bases: primerSeq,
+      start: start,
+      end: end,
+      fullSequence,
+      primerBindsOn: "3prime",
+      sequenceLength: fullSequence.length
+    }));
+    expected = [false, true, true, true];
+    assert.deepEqual(
+      allBasesWithMetaData.map(({ isMatch }) => isMatch),
+      expected
+    );
+  });
+  it("works for non fully-overlapping non origin-spanning case binding on 3prime", () => {
+    const fullSequence = "ACGTCCACGT";
+    let primerSeq = "aaaaACGT";
+    const start = 0;
+    const end = 3;
+    let { allBasesWithMetaData } = getStructuredBases({
+      annotationRange: { start, end },
+      forward: true,
+      bases: primerSeq,
+      start: start,
+      end: end,
+      fullSequence,
+      primerBindsOn: "3prime",
+      sequenceLength: fullSequence.length
+    });
+
+    let expected = [false, false, false, false, true, true, true, true];
+    assert.deepEqual(
+      allBasesWithMetaData.map(({ isMatch }) => isMatch),
+      expected
+    );
+    expected = [
+      undefined,
+      undefined,
+      undefined,
+      undefined,
+      false,
+      false,
+      false,
+      false
+    ];
+    assert.deepEqual(
+      allBasesWithMetaData.map(({ isAmbiguousMatch }) => isAmbiguousMatch),
+      expected
+    );
+
+    primerSeq = "aaaaCCGT";
+    ({ allBasesWithMetaData } = getStructuredBases({
+      annotationRange: { start, end },
+      forward: true,
+      bases: primerSeq,
+      start: start,
+      end: end,
+      fullSequence,
+      primerBindsOn: "3prime",
+      sequenceLength: fullSequence.length
+    }));
+    expected = [false, false, false, false, false, true, true, true];
+    assert.deepEqual(
+      allBasesWithMetaData.map(({ isMatch }) => isMatch),
+      expected
+    );
+    expected = [
+      undefined,
+      undefined,
+      undefined,
+      undefined,
+      false,
+      false,
+      false,
+      false
+    ];
+    assert.deepEqual(
+      allBasesWithMetaData.map(({ isAmbiguousMatch }) => isAmbiguousMatch),
+      expected
+    );
+  });
+  it("works for non fully-overlapping non origin-spanning case binding on 5prime", () => {
+    const fullSequence = "ACGTCCACGT";
+    let primerSeq = "ACGTaaaa";
+    const start = 0;
+    const end = 3;
+    let { allBasesWithMetaData } = getStructuredBases({
+      annotationRange: { start, end },
+      forward: true,
+      bases: primerSeq,
+      start: start,
+      end: end,
+      fullSequence,
+      primerBindsOn: "5prime",
+      sequenceLength: fullSequence.length
+    });
+
+    assert.deepEqual(
+      allBasesWithMetaData.map(({ isMatch }) => isMatch),
+      [true, true, true, true, false, false, false, false]
+    );
+    assert.deepEqual(
+      allBasesWithMetaData.map(({ isAmbiguousMatch }) => isAmbiguousMatch),
+      [false, false, false, false, undefined, undefined, undefined, undefined]
+    );
+
+    primerSeq = "CCGTaaaa";
+    ({ allBasesWithMetaData } = getStructuredBases({
+      annotationRange: { start, end },
+      forward: true,
+      bases: primerSeq,
+      start: start,
+      end: end,
+      fullSequence,
+      primerBindsOn: "5prime",
+      sequenceLength: fullSequence.length
+    }));
+    assert.deepEqual(
+      allBasesWithMetaData.map(({ isMatch }) => isMatch),
+      [false, true, true, true, false, false, false, false]
+    );
+    assert.deepEqual(
+      allBasesWithMetaData.map(({ isAmbiguousMatch }) => isAmbiguousMatch),
+      [false, false, false, false, undefined, undefined, undefined, undefined]
+    );
+  });
+  it("works for origin-spanning case", () => {
+    const fullSequence = "ACGTCCACGT";
+    let primerSeq = "TACGT";
+    const start = 9;
+    const end = 3;
+    let { allBasesWithMetaData } = getStructuredBases({
+      annotationRange: { start, end },
+      forward: true,
+      bases: primerSeq,
+      start: start,
+      end: end,
+      fullSequence,
+      primerBindsOn: "3prime",
+      sequenceLength: fullSequence.length
+    });
+    let expected = [true, true, true, true, true];
+    assert.deepEqual(
+      allBasesWithMetaData.map(({ isMatch }) => isMatch),
+      expected
+    );
+    primerSeq = "AACGT";
+    expected = [false, true, true, true, true];
+    ({ allBasesWithMetaData } = getStructuredBases({
+      annotationRange: { start, end },
+      forward: true,
+      bases: primerSeq,
+      start: start,
+      end: end,
+      fullSequence,
+      primerBindsOn: "3prime",
+      sequenceLength: fullSequence.length
+    }));
+    assert.deepEqual(
+      allBasesWithMetaData.map(({ isMatch }) => isMatch),
+      expected
+    );
+  });
+});
diff --git a/packages/ove/demo/src/exampleData/exampleSequenceData.js b/packages/ove/demo/src/exampleData/exampleSequenceData.js
index 7edb6070..d9f2b477 100644
--- a/packages/ove/demo/src/exampleData/exampleSequenceData.js
+++ b/packages/ove/demo/src/exampleData/exampleSequenceData.js
@@ -28,28 +28,98 @@ export default {
     }
   ],
   primers: [
+    // {
+    //   name: "Example Primer 1",
+    //   start: 280,
+    //   end: 300,
+    //   type: "primer_bind",
+    //   forward: true
+    // },
+    // {
+    //   name: "Blue primer",
+    //   start: 1,
+    //   end: 20,
+    //   type: "primer_bind",
+    //   forward: true,
+    //   color: "blue"
+    // },
+    // {
+    //   name: "Red primer",
+    //   start: 21,
+    //   end: 30,
+    //   type: "primer_bind",
+    //   forward: true,
+    //   color: "red"
+    // },
+    // {
+    //   name: "Normal primer",
+    //   start: 1,
+    //   end: 4,
+    //   type: "primer_bind",
+    //   forward: true,
+    //   color: "blue",
+    //   primerBindsOn: '3prime',
+    //   bases: "acgt"
+    // },
     {
-      name: "Example Primer 1",
-      start: 280,
-      end: 300,
+      name: "Origin-spanning primer",
+      start: 5297,
+      end: 4,
       type: "primer_bind",
-      forward: true
+      forward: true,
+      color: "red",
+      primerBindsOn: "3prime",
+      bases: "tcgacgt"
     },
     {
-      name: "Blue primer",
-      start: 1,
-      end: 20,
+      name: "Origin-spanning reverse primer",
+      start: 5297,
+      end: 4,
+      type: "primer_bind",
+      forward: false,
+      color: "red",
+      primerBindsOn: "3prime",
+      bases: "acgtcga"
+    },
+    {
+      name: "Left tail primer",
+      start: 7,
+      end: 10,
       type: "primer_bind",
       forward: true,
-      color: "blue"
+      color: "red",
+      primerBindsOn: "3prime",
+      bases: "aaaatatg"
     },
     {
-      name: "Red primer",
-      start: 21,
-      end: 30,
+      name: "Right tail primer",
+      start: 11,
+      end: 14,
       type: "primer_bind",
       forward: true,
-      color: "red"
+      color: "red",
+      primerBindsOn: "5prime",
+      bases: "acaaaaaa"
+    },
+    {
+      name: "Left tail primer - reverse",
+      start: 21,
+      end: 24,
+      type: "primer_bind",
+      forward: false,
+      color: "red",
+      primerBindsOn: "3prime",
+      bases: "aaaaagcc"
+    },
+    {
+      name: "Right tail primer - reverse",
+      start: 40,
+      end: 43,
+      type: "primer_bind",
+      forward: false,
+      color: "red",
+      primerBindsOn: "5prime",
+      bases: "aagaaaaa"
     }
   ],
   afeatures: [
diff --git a/packages/ove/src/RowItem/StackedAnnotations/getStructuredBases.js b/packages/ove/src/RowItem/StackedAnnotations/getStructuredBases.js
index 13441fa1..a1ed494d 100644
--- a/packages/ove/src/RowItem/StackedAnnotations/getStructuredBases.js
+++ b/packages/ove/src/RowItem/StackedAnnotations/getStructuredBases.js
@@ -4,7 +4,7 @@ import { getComplementSequenceString } from "@teselagen/sequence-utils";
 import { bioData } from "@teselagen/sequence-utils";
 const { ambiguous_dna_values } = bioData;
 export function getStructuredBases({
-  annotationRange,
+  // annotationRange,
   forward,
   bases = "",
   start,
@@ -29,9 +29,8 @@ export function getStructuredBases({
     }
   }
   const aRange = {
-    //tnr: this probably needs to be changed in case annotation wraps origin
-    start: annotationRange.start - start,
-    end: annotationRange.end - start
+    start: 0,
+    end: annLen - 1
   };
   const r = {
     aRange,
@@ -63,7 +62,7 @@ export function getStructuredBases({
     forward ? r.basesNoInserts : r.basesNoInserts.split("").reverse().join("")
   );
   r.basesNoInsertsWithMetaData = basesForRange.split("").map((b, i) => {
-    const indexOfBase = i + annotationRange.start;
+    const indexOfBase = (i + start) % sequenceLength;
     let seqForBase = (fullSequence && fullSequence[indexOfBase]) || "";
     if (!forward) {
       seqForBase = getComplementSequenceString(seqForBase);
@@ -92,6 +91,5 @@ export function getStructuredBases({
         ...bases.split("").map(b => ({ b, isMatch: false }))
       );
     });
-
   return r;
 }