This is because the gene for blue eyes is recessive and both copies for that code for blue eyes must be present before that characteristic can be expressed.
(This; is; because the gene for blue eyes is recessive and both copies for that code for blue eyes must be present) (the gene for blue eyes; is; recessive) (both copies for that code for blue eyes; must be; present; T:before that characteristic can be expressed) (that characteristic; can be expressed; )
This the gene for blue eyes both copies for that code for blue eyes that characteristic
is is must be can be expressed
because the gene for blue eyes is recessive and both copies for that code for blue eyes must be present
recessive
present T:before that characteristic can be expressed