Which of the following statements are correct regarding genetic disorders?

1. Phenylketonuria is an autosomal recessive disorder caused by the inability to convert phenylalanine into tyrosine.
2. Haemophilia is an autosomal recessive disorder affecting blood clotting.
3. Thalassemia is caused by the deletion or mutation in globin genes and affects the synthesis of hemoglobin.
4. Sickle-cell anemia is caused by the substitution of valine by glutamic acid at the sixth position of the beta-globin chain.