Well they do not really bar each other. You need to create one new column for gender ratio and two columns for itemdrop. In adopt.php, the sql insert line will become something like this(assuming you add gender ratio column first):
PHP Code:
$mysidia->db->insert("adoptables", array("id" => NULL, "type" => $mysidia->input->post("type"), "class" => $mysidia->input->post("class"), "description" => $mysidia->input->post("description"), "eggimage" => $eggimage, "whenisavail" => $mysidia->input->post("cba"),
"alternates" => $mysidia->input->post("alternates"), "altoutlevel" => $mysidia->input->post("altoutlevel"), "altchance" => $mysidia->input->post("altchance"), "shop" => $mysidia->input->post("shop"), "cost" => $mysidia->input->post("cost"),
"genderratio" => $mysidia->input->post("genderratio"), "dropitem" => $mysidia->input->post("dropitem"), "droprate" => $mysidia->input->post("droprate")));
Of course you still need to modify the adoptable creation form, this should be easy.