Video Transcript
What is the meaning of the term
autosome? A chromosome that has been
automatically replicated, ready for cell division. Any chromosome that has had a
section removed. A chromosome that is found in the
gametes of a human. Any chromosome that is not a sex
chromosome, X or Y. Or a chromosome that is
automatically destroyed when damaged.
This question asked us to select
the most appropriate definition for the term autosome. So what is an autosome? In human somatic cells, that is,
any cell except for egg cells in females and sperm cells in males, there are 46
chromosomes. The chromosomes are found in the
nucleus of the cells and can be organized into 23 pairs. One chromosome in each pair was
inherited from the biological mother and the other inherited from the biological
father. In this diagram, fuchsia represents
chromosomes inherited from the mother and orange from the father.
You will notice from the diagram
that in 22 of these pairs, each chromosome in the pair is the same length as the
other. We say they are homologous
chromosomes. Homologous chromosomes are pairs of
chromosomes of similar length. They have the same genes at each
location. And following replication, the
centromere will be at the same position on each chromosome in the pair. In this diagram, the homologous
pairs one to 22 are autosomes. The final pair number 23 are not
autosomes. These are the sex chromosomes.
There are two different sex
chromosomes, the X chromosome and the Y chromosome. And although they do form a pair,
you will notice that in our diagram they are not homologous. We have one X chromosome and one Y
chromosome in our example. Let’s have a closer look at those
sex chromosomes. The X chromosome is very large with
around 900 genes. In comparison, the Y chromosome is
very small with only around 55 genes. In our example, the cell contains
one X and one Y chromosome. This means the cells belong to a
male. In most female somatic cells, there
are two X chromosomes. The sex chromosomes help determine
the sex-specific features in both males and females.
We have just seen how chromosomes
in cells can be autosomes or sex chromosomes. We now have enough information to
answer our question. We know that any chromosome that is
not an X or a Y is called an autosome. The correct answer to the question
“What is the meaning of the term autosome?” is any chromosome that is not a sex
chromosome, X or Y.
