Video Transcript
Which of the following statements
about human chromosomes is true? (A) Each chromosome in a somatic,
also known as a body, cell contains the entire human genome. (B) All chromosomes are the same
size and contain the same number of genes. (C) Somatic, also known as body,
cells contain half the number of chromosomes that a gamete or sex cell contains. Or (D) a single chromosome can
carry hundreds to thousands of genes.
Three of these four statements are
false, and we’re looking for the one that’s true regarding human chromosomes. So, what is a chromosome
exactly? Each human body cell or somatic
cell contains all the genetic information that’s necessary to make a human. This genetic information is stored
in the nucleus of cells in the form of compacted DNA. This molecule is not continuous
though. In humans, it’s actually segmented
into 46 pieces called chromosomes. These 46 chromosomes represent all
the genetic information in our cells, which we call the human genome. So, we can already eliminate this
statement because the entire genome is contained not in a single chromosome, but in
a set of these 46 chromosomes.
These 46 chromosomes are arranged
into 23 pairs of chromosomes. Chromosomes one to 22 are arranged
based on their size, with chromosome one being the largest and chromosome 22 being
the smallest. The 23rd pair of chromosomes, made
up of chromosomes X and Y, represent the sex chromosomes, which are responsible for
determining the biological sex of the person. Chromosomes within a pair carry a
very similar number of genes. Genes are sections of chromosomes
that code for a functional unit, such as a protein. The largest of them, chromosome
one, carries just over 2000 genes, while chromosome 22, the smallest, contains about
500 genes. We can then eliminate this answer
choice because all chromosomes aren’t necessarily the same size or contain the same
number of genes.
Besides body or somatic cells, the
human body can also produce sex cells. These sex cells, also called
gametes, do not contain 46 chromosomes. Instead, they only contain one
chromosome from each pair, so just 23 in total. This is so that when the sex cells
combine during fertilization, the resulting embryo has the correct number of
chromosomes in each of their cells, or 46 in total. So, this statement is also
incorrect because it’s the gametes that contain half the number of chromosomes, not
the somatic cells. This then leaves this statement,
which is true because chromosomes can contain hundreds to thousands of genes.
