Edit in JSFiddle

$(document).ready(function(){
    $('#btnAddToBegining').click(function(){
      $("#ddlList").prepend("<option value='0' selected='selected'> Select </option>");
    });
    
     $('#btnAddToEnd').click(function(){
        $("<option value='6'>Java Script</option>").appendTo("#ddlList");
    });       
});

<select id="ddlList">
  <option value="1">ASP.NET</option>
  <option value="2">C#</option>
  <option value="3">VB.NET</option>
  <option value="4">HTML</option>
  <option value="5">jQuery</option>
</select>

<br/><br/>
<input type="button" id="btnAddToBegining" Value="Add Item to Begining" />
&nbsp;&nbsp;
<input type="button" id="btnAddToEnd" Value="Add Item to End" />