(a) Description/information. Compared to a female ovum, a sperm cell
is very small, but it is well shaped to reach out and penetrate a female ovum. A sperm
cell has a head, a middle section, and a tail (figure 1-5). The head is flat and oval
shaped (ideal for penetration and attachment) and contains the nucleus of the cell. The
middle section is made up of substances that make useable energy to propel the tail.
And the long tail acts like a whip to move the sperm. When the head penetrates the
ovum, the tail separates from the rest of the sperm.
Figure 1-5. Structure of a sperm cell.
(b) Chromosomes in a sperm cell. The nucleus in the head of a sperm
cell contains chromosomes. A mature sperm has 23 chromosomes. An immature
sperm cell has 46 chromosomes, one an X (female) chromosome and the other a Y
(male) chromosome. A reduction division takes place to form a mature cell which has
23 chromosomes. At that time, an X chromosome (female) goes to one sperm cell, and
a Y (male) chromosome goes to the other sperm cell. If an ovum is joined by a sperm
with an X chromosome, the combination will form a female. If a sperm with a Y
chromosome joins an ovum, a male is formed.