Video Transcript
A human has 46 chromosomes in a
diploid body cell. How many chromosomes will a haploid
cell from this organism contain?
Chromosomes are the structures
within humans that contain our genetic information in the form of genes. These genes contain the
instructions to produce functional units, for instance, proteins. The majority of the cells in a
human are diploid. A diploid cell has two copies of
each chromosome. The di- in “diploid” actually means
two.
Let’s take a look at a karyotype of
a diploid human cell. In a human body cell, one
chromosome in each homologous chromosome pair will have been inherited from the
individual’s biological mother. The other chromosome in each
chromosome pair will have been inherited from the individual’s biological
father.
Chromosomes one to 22 are called
autosomes. Because these chromosomes come in
homologous pairs, a typical human body cell will contain 44 autosomes in total. The remaining chromosomes are sex
chromosomes. In humans, males typically have the
combination XY and females the combination XX.
Not all cells in the human body are
diploid; gametes, or sex cells, are haploid. This means they contain half the
genetic material of a diploid cell, as they only have a single set of
chromosomes. This is so when a sperm and egg
cell combine during fertilization, the resulting zygote has the correct number of
chromosomes.
Let’s take a closer look at a
karyotype of a haploid cell, in this case an egg cell or ovum. In this gamete, there are 22
autosomes and only one sex chromosome. We can see from the karyotypes that
to convert from a diploid cell to a haploid cell, we need to divide the number of
chromosomes by two. There are 46 chromosomes in a human
diploid body cell, so dividing 46 by two gives us the correct answer.
A haploid cell from a human will
contain 23 chromosomes.
