Video Transcript
The diagram provided shows how eye
color can be inherited in humans. What term is given to the gene that
produces blue eyes in this example? (A) Dominant, (B) submissive, (C)
inactive, (D) recessive, or (E) passive.
In this example, we can see that
the mother has the gene for blue eyes, and she has two copies, represented here by
these blue bands, whereas the father has the gene for brown eyes. And he has two copies of it,
represented here by these brown bands. The child inherits one copy of the
gene for blue eyes and one copy of the gene for brown eyes.
However, the child only expresses
the gene for brown eyes. The brown eye trait is dominant,
meaning that this version of the eye color gene will always be expressed as long as
it’s present. Here, we’ll write two uppercase Bs
to indicate that there are two copies of this dominant gene for brown eyes. And the blue eye trait is
recessive, meaning that this version of the eye color gene will only be expressed if
there isn’t a dominant version of the gene present. Here, we’ll write two lowercase b’s
to indicate that there are two copies of this recessive gene for blue eyes.
In the child, there is one copy of
the dominant brown eye gene, shown as uppercase B, and one copy of the recessive
blue eye gene, shown as lowercase b. Because we have a copy of each and
we only see the brown eye color in the child, the brown eye color gene must be
dominant and the blue eye color gene must be recessive. Therefore, the term given to the
gene that produces blue eyes in this example is (D) recessive.
