Why do we need chromosomes?

Our DNA usually hangs around in the nucleus – 46 long strings that seem to be all tangled up in a mess. Then lo and behold, these long strings fold up and become chromosomes. Why is this so?

Bill Earnshaw’s lab at Edinburgh University does some amazing work with chromosomes and cell division. He can explain to us very elegantly why we need chromosomes in this video.

[Bill Earnshaw – Biological Sciences from Research in a Nutshell on Vimeo.]

It’s all about helping the DNA get shared equally between two new daughter cells when the cell divides. It’s easier to divide a tangle of wool into two if you untangle it and roll it up into balls first.

DNA carries genes and makes up the blueprint that’s responsible for making every cell, every tissue, every organ work properly, communicate with each other, and making each of us unique. So it’s important we have the right set of genes.

Cells divide a lot – millions of our cells divide every minute.

Here are some photos of the chromosomes doing their thing during cell division, from the Earnshaw lab. The colour is from fluorescent dyes that can tell the different structures apart.

In the photo above the chromosomes are lining up along the middle of the cell (the “equator” or “metaphase plate”) of the dividing cell (this stage is “metaphase”). When they’re all lined up correctly the next stage can start:

The photo above shows the blue chromosomes moving along the green spindle fibres in opposite directions (this stage is “anaphase”). Each set of chromosomes will belong to one of the two new daughter cells. If this happens correctly the chromosomes have done their job (scientists call it mitosis) and both new cells have identical sets of DNA.

(This is cross-posted from chromosomesandcancer.com.)