Video Transcript
A human ovum contains 24
chromosomes. It is fertilized by a sperm cell
with the normal number of chromosomes. Which of the following is true
about the zygote that will develop? (A) The zygote will contain the
normal number of chromosomes, but these chromosomes will not pair correctly. (B) The zygote will fail to develop
into an embryo. (C) The zygote will contain one too
many chromosomes. Or (D) the zygote will contain an
additional pair of chromosomes.
Sperm and egg cells are gametes,
which means they are haploid. Haploid cells contain half the
number of chromosomes than all other cells in the body. In humans, we contain 46
chromosomes in our body cells and 23 chromosomes in our gametes. When the egg and sperm join by
fertilization, they produce a zygote with a full set of 46 chromosomes.
However, in this question, the egg
cell has 24 chromosomes instead of 23. This extra chromosome is often due
to an error in meiosis, the type of cell division that makes gametes. So, after fertilization of an ovum
with 24 chromosomes with a sperm cell with 23 chromosomes, a zygote with 47
chromosomes is the result. This zygote will contain one extra
chromosome and have 47 chromosomes instead of the normal 46. Therefore, answer choice (C) is the
correct choice. The zygote will contain one too
many chromosomes.
