Video Transcript
If you cross two different breeds
of cats, you get kittens with a combination of characteristics, some from their
mother and some from their father. What makes this possible? (A) Half of the litter of kittens
receives the father’s DNA and the other half receives the mother’s DNA. (B) Each kitten does not receive
the same amount of DNA from each parent. (C) This is not possible; all the
kittens are identical to one of their parents. Or (D) each kitten receives half of
its DNA from each of its parents.
This question asks about how
genetic material is passed down from parents. So let’s look at how sexual
reproduction occurs in these cats. In most of the mothers’ and
fathers’ body cells, there are two copies of their DNA. You can see these two copies as the
two X-shaped chromosomes in each cell. Body cells are diploid, because di-
means two, and they have two sets of chromosomes.
Through the process of meiosis, the
mother and father can create sex cells, like the egg and sperm cell. These can be used to create
offspring. Notice that these have half the
number of chromosomes as the body cells. So, when the sperm fertilizes the
egg, an embryo is created that has the full amount of the chromosomes as the
parents.
Therefore, each kitten receives
half of their DNA from each parent. So the correct answer is (D). Each kitten receives half of its
DNA from each of its parents.
