Video Transcript
How do the structures of the X and
Y chromosomes in humans differ? (A) The X chromosome contains less
than 50 percent of the genes found on the Y chromosome. (B) The X chromosome is much
shorter than the Y chromosome. (C) The Y chromosome is much
shorter than the X chromosome. (D) The Y chromosome is much wider
than the X chromosome. (E) There is no difference in the
structure between the X and Y chromosomes.
To answer this question, we need to
recall what we know about the X and Y chromosomes in humans. Then, we’ll be able to evaluate and
eliminate answer choices to identify the correct one.
Human somatic cells are diploid and
contain 46 chromosomes, which are organized into 23 homologous pairs. The term “homologous” means that
the chromosomes have similar lengths, the same genes, and the same centromere. The first 22 pairs of chromosomes
are called autosomes and look similar in male and female cells. In the word “autosome,” the prefix
auto- means self and the suffix -some means body.
The 23rd pair of chromosomes are
not homologous chromosomes like the autosomes. This is because the 23rd pair of
chromosomes are the sex chromosomes. In humans and most other mammals,
there are two types of sex chromosomes, the X and the Y chromosome, which are used
to determine biological sex.
Unlike the autosomes, there are
several differences in the X and the Y sex chromosomes. The X chromosome is very long in
length compared to the Y chromosome and contains about 900 genes. The Y chromosome, however, is very
short in length compared to the X chromosome and only contains around 55 genes.
Now, using the information we just
recalled, we can evaluate the answer choices. We mentioned that the X and the Y
chromosome are not homologous, which means they are not the same lengths, they
contain different genes, and they have different centromeres. More specifically, we recall that
the X chromosome is much longer in length than the Y chromosome and contains about
845 more genes.
With this information, we’re able
to answer the question. The structures of the X and Y
chromosomes in humans differ because the Y chromosome is much shorter than the X
chromosome.
