Edit in JSFiddle

var base = {
    productFilterSetup: function() {
        $('.productFilter').each(
        function() {
            var tmp = new base.filterGroup(this);
            tmp.setup();
        });
    },
    filterGroup: function(filter_group) {
        var me = this;
        me.target_element = filter_group;
        me.active_element_index = 0;
        me.setup = function() {
            $(filter_group).find('input[type=radio]').bind('click', function() {
                me.update(this);
            });
        };
        me.update = function(target_radio) {
            var fieldsets = $(me.target_element).find('fieldset'),
                len = fieldsets.length,
                i = 0,
                j = 0,
                radios, 
                radios_len, 
                options = [],
                options_buffer = '',
                num_of_steps = 0;

            for (i = 1; i <= num_of_steps + 1; i += 1) {
                if ($('fieldset.step' + i).length > 0) {
                    num_of_steps += 1;
                }
            }

            for (i = 0; i < num_of_steps; i += 1) {
                if ($(target_radio).parents('fieldset.step' + (i + 1)).length > 0) {
                    for (j = i; j < num_of_steps; j += 1) {
                        $('fieldset.step' + (j + 2) + ' input[type=radio]').attr('checked', false);
                    }
                }
            }

            for (i = 0; i < len; i += 1) {
                radios = $(fieldsets[i]).find('input[type=radio]');
                radios_len = radios.length;
                for (j = 0; j < radios_len; j += 1) {
                    if ($(radios[j]).is(':checked')) {
                        options.push(j + 1);
                    }
                }
            }
            fieldsets.addClass('hide');
            $('fieldset.option0').removeClass('hide');
            for (i = 0; i < options.length; i += 1) {
                options_buffer += options[i];
                $('fieldset.option' + options_buffer).removeClass('hide');
            }
        };
    }
};

$(
function() {
    base.productFilterSetup();
});

<form action="#" id="unique_id" class="productFilter">
    <fieldset class="step1 option0">
        <legend>Lorizzle ipsizzle (Q1)</legend>
        <p>
            <input id="question_1" name="group_1" type="radio" />
            <label for="question_1">Yes!</label>
        </p>
        <p>
            <input id="question_2" name="group_1" type="radio"/>
            <label for="question_2">No.</label>
        </p>
    </fieldset>
    <fieldset class="hide step2 option1">
        <legend>Sizzle pizzle (Branch 1)</legend>
        <p>
            <input id="question_1_1" name="group_2" type="radio" />
            <label for="question_1_1">True</label>
        </p>
        <p>
            <input id="question_1_2" name="group_2" type="radio" />
            <label for="question_1_2">False</label>
        </p>
    </fieldset>
    <fieldset class="hide step2 option2">
        <legend>Grizzle fipdizzle (Branch 2)</legend>
        <p>
            <input id="question_2_1" name="group_3" type="radio" />
            <label for="question_2_1">True</label>
        </p>
        <p>
            <input id="question_2_2" name="group_3" type="radio" />
            <label for="question_2_2">False</label>
        </p>
    </fieldset>
    <fieldset class="hide step3 option11">
        <legend>Suscipizzle lorizzle (Branch 1 1)</legend>
        <p>
            <input id="question_1_1_1" name="group_4" type="radio"/>
            <label for="question_1_1_1">Yea</label>
        </p>
        <p>
            <input id="question_1_1_2" name="group_4" type="radio"/>
            <label for="question_1_1_2">Nay</label>
        </p>
    </fieldset>
    <fieldset class="hide step3 option12">
        <legend>Suscipizzle izzle (Branch 1 2)</legend>
        <p>
            <input id="question_1_2_1" name="group_5" type="radio"/>
            <label for="question_1_2_1">Yea</label>
        </p>
        <p>
            <input id="question_1_2_2" name="group_5" type="radio" />
            <label for="question_1_2_2">Nay</label>
        </p>
    </fieldset>
    <fieldset class="hide step3 option21">
        <legend>Macdizzle ma nizzle (Branch 2 1)</legend>
        <p>
            <input id="question_2_1_1" name="group_6" type="radio" />
            <label for="question_2_1_1">Yea</label>
        </p>
        <p>
            <input id="question_2_1_2" name="group_6" type="radio" />
            <label for="question_2_1_2">Nay</label>
        </p>
    </fieldset>
    <fieldset class="hide step3 option22">
        <legend>Shizzle bizzle (Branch 2 2)</legend>
        <p>
            <input id="question_2_2_1" name="group_7" type="radio" />
            <label for="question_2_2_1">Yea</label>
        </p>
        <p>
            <input id="question_2_2_2" name="group_7" type="radio" />
            <label for="question_2_2_2">Nay</label>
        </p>
    </fieldset>
</form>
<p>Lorizzle ipsizzle doggy sit amizzle, shizzlin dizzle adipiscing nizzle. Nullizzle sapien velizzle, nizzle break yo neck, yall, suscipizzle da bomb, dizzle vizzle, sheezy.</p>
<a title="A button, fo shizzle." href="#" class="buttonGreen"><span>Click me. Do it. Now!</span></a>

fieldset {margin:10px 0;}
.hide {display:none;}