Studi kekerabatan ayam ketawa (gallus gallus domestics LINNAEUS, 1758) berdasarkan morfometrik pita suara dan analisis gen IGF-1 (insulin-like growth factor-1) = Study of relationship the gaga chicken (gallus gallus domesticus LINNAEUS, 1758) dangdut and slow type base on morphometric vocal cord and IGF-1 (Insulin-Like Growth Factor-1) gene analysis