diff --git a/functions/funGCcontent.js b/functions/funGCcontent.js
new file mode 100644
index 0000000..88eda95
--- /dev/null
+++ b/functions/funGCcontent.js
@@ -0,0 +1,9 @@
+function funGCcontent(parms){
+    parms = parms||{
+        sequence:'AGAAGGAAAACGGGAAACTTCACAATTAGTGAATATTTAAAAACAGACTCTTAAGAAACCAAAGGATCAAGGAAGATACCACAGGGAAAAATAGAGAATA'
+    }
+    // calculate GC funGCcontent
+    let GClength = parms.sequence.toUpperCase().split('').filter(x=>(x=='G'|x=='C')).length
+    let seqLength = parms.sequence.length
+    return `GC content is ${GClength}/${seqLength} = ${GClength/seqLength}`
+}