Video Transcript
Which of the following Punnett
squares shows the correct inheritance of sex in humans? (A), (B), (C), or (D).
The 23rd pair of chromosomes in
humans is referred to as the sex chromosomes. Biological females inherit two X
chromosomes for this set, while biological males inherit one X from their biological
mother and one Y from their biological father.
Let’s look at how this would appear
in a Punnett square. Since the biological male genotype
for these chromosomes is XY, the biological father’s genotype would be XY. Likewise, since the biological
female genotype for these chromosomes is XX, the biological mother’s genotype would
be XX. When we fill out a Punnett square,
we combine the letter from the row header with the letter from the column
header. So if we fill out the rest of the
Punnett square by the same method, we should end up with this. Basically, biological females
receive an X from both parents, while biological males receive an X from their
mothers and a Y from their fathers.
If we look through the answer
choices to find the best match to this Punnett square, we can see it is (D). The Punnett square that shows the
correct inheritance of sex in humans is the one that shows biological female gametes
as XX, biological male gametes as XY, and the offspring accurately corresponding to
that.
