working (sort of) gene block

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://d3js.org/d3.v4.min.js"></script>
  <style>
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
  </style>
</head>

<body>
  <script>
    var svg = d3.select("body").append("svg")
      .attr("width", 960)
      .attr("height", 500)

d3.json("data.json", function(err, mydata) {
      var g = d3.select("svg").selectAll("rect")
        .data(mydata)
      	.enter()
      	.append("g")
      	.attr("transform", function (d) {
          if (d.orientation === 'forward') {
            return "translate( "+ d.start + ",100");
          }
          else {
            return "translate(" + d.start + ",125)";
          }
        }];
      	g.append("rect")
        g.append("text")
      	.attr("y", function (d) {
        	if (d.orientation == "forward") {
            return 100;
          }
        	else if (d.orientation == "reverse") {
            return 125;
          }
      })
      	.attr("height", 50)
      	.attr("x", function (d) {
        	return d.start;
      	})
      	.attr("width", function (d) {
        	return d.stop - d.start;
        })
      	.attr("stroke", "#000814")
      	.attr("stroke-width", 3)
      	.attr("fill", function(d) {
        	if (d.orientation == "forward") {
          	return "green";  
          }
        	else if (d.orientation == "reverse") {
            return "red";
          }
     
      });
    })

</script>    
</body>

https://d3js.org/d3.v4.min.js