Video Transcript
Sperm samples from farm animals can
be separated into X- and Y-chromosome-containing sperm cells and stored in liquid
nitrogen until needed. In which situation might this
procedure be beneficial to farmers? (A) To prioritize milk production
in cattle by using sperm cells containing Y chromosomes. (B) To prioritize milk production
in cattle by using sperm cells containing X chromosomes. (C) To prioritize milk production
in sheep by using sperm cells containing Y chromosomes. (D) To prioritize meat production
in cattle by using sperm cells containing X chromosomes. (E) To prioritize meat production
in sheep by using sperm cells containing X chromosomes.
This question asks why the
separation of sperm cells might be beneficial to farmers. Biological sex is determined by the
presence of the sex chromosomes. Two copies of X produces a
biological female, while one copy of X and Y produces a biological male. When the egg and sperm cells are
formed, they receive half the number of chromosomes as a normal body cell. So, egg cells will contain only X
chromosomes, while sperm cells will contain either an X or Y chromosome.
So, when the sperm cell fertilizes
an egg, either an X or Y chromosome in the sperm will combine with an X chromosome
from the egg. You can see this here, where female
offspring are produced from a sperm cell containing an X chromosome. And you can see this here, where
male offspring are produced from a sperm that contain a Y chromosome.
Therefore, the sperm determines the
biological sex of the offspring. Sperm with an X chromosome can be
sorted and separated from sperm with a Y chromosome. This is because X-containing sperm
have more DNA than Y-containing sperm, since the X chromosome is larger than the Y
chromosome.
This is useful for those who farm
cattle to produce milk, because female cattle are primarily used for milk
production. In this case, sperm with X
chromosomes would be used to inseminate female cattle. The resulting offspring would then
be female and could produce milk.
Therefore, the correct answer
choice is (B), to prioritize milk production in cattle by using sperm cells
containing X chromosomes.
