Explain how 3 meters of DNA can fit inside the microscopic nucleus of a microscopic cell.

Answer 1

Let's use an analogy to help understand and answer this question. Let's imagine a spool of thread. A spool is a plastic or wooden cylinder. Thread (like using for sewing) normally gets wound/wrapped around a spool in order to keep the thread neat and prevent it from being tangled. A spool of thread, which you can hold in the palm of your hand, can hold a about 250 yards of thread! That's quite a lot of thread in a very small space!

Similarly, DNA gets wound around proteins called histones. These histones act very similarly to the spool for the thread. The DNA, like microscopic thread, can be wound over and over around these histones. Then, the histones can be stacked in groups of 8 to form what's called a nucleosome. (So imagine a small cube of 8 spools of threads; 4 spools on the top, 4 on the bottom). Then, the nucleosomes can be combined for form filaments and eventually, they will form chromosomes.

This is how lots of DNA can be compacted into a very small space.

If you'd like a diagram/illustration, please refer to this one made by the National Human Genome Research Institute: https://www.genome.gov/sites/default/files/tg/en/illustration/histones.jpg

For more information about histones, please visit this page: https://www.genome.gov/genetics-glossary/histone