I’m not just here for fun though. I’m escorting a group of University of New England biomedical science students on a study tour, so I have to balance work and play. 

Our first days have been spent delving into the world of cytogenetics. Cytogenetics is the study of chromosomes and disease.

Without realising it, you probably already know a little bit about cytogenetics. Most people will have heard of Down Syndrome, and know that it is caused by having an extra chromosome. In general, humans have 23 pairs of chromosomes, for a total of 46 chromosomes altogether.

But sometimes, instead of having this normal number, people can instead end up with an extra chromosome, like in Down Syndrome, or sometimes they can be missing a chromosome altogether.

Most of the time having an extra chromosome is fatal. But there are some special cases where people with 47 chromosomes survive.

Down Syndrome is obviously one of these, where people have an extra copy of chromosome 21. Edwards Syndrome is another rarer example, where people have a third copy of chromosome 18. Rarer still is Patau Syndrome, or having an extra copy of chromosome 13.

Some people can even have extra copies of the sex chromosomes.

Missing a chromosome is also usually fatal. The exception here is a condition called Turners Syndrome, where women only have one sex chromosome, a single X chromosome, instead of a pair. 

So how do we know if someone has an extra, or a missing chromosome? Well, there are usually some clues. People with these disorders usually have some changes to their physical appearance, and usually they may have learning difficulties or some mental impairment. But as our students have learnt this week, the only way to really tell for sure is to do some cytogenetic testing.

To see if someone has an unusual number of chromosomes we really need to look inside their cells and count. The cells can then be stained with a special dye, and looked at under a microscope. They can be counted, and sorted into pairs, to see if there are more or less than the usual number.

But why does it cause a problem to have too many or too few chromosomes? Our chromosomes contain the information to make all the different proteins that our cells need. But if we have an extra chromosome we make too much protein, while if we are missing a chromosome we don’t make enough. 

Just as it’s important to have balance in the rest of our lives, it’s also important to have balance in our chromosomes. Not too many, not too few, just the right amount.