Saturday, January 16, 2016

Human Chromosome vs. Human Nucleus

I made this image to use in my genetics class.  In the center is an image of a human cheek cell stained with methylene blue.  The line running around the cell shows the length of human chromosome 21 (the smallest chromosome) relative to the cheek cell.  (Click the image for a larger view.)

Check out Part II of this post to see how this image would look with the biggest chromosome in the human nucleus (chromosome 1).

Pretty cool! The nucleus looks so tiny. And of course there's not one but two copies of chromosome 21 packed in there. And 44 other chromosomes too...all of which are longer than chromosome 21. Chromosome 1, the longest human chromosome, is 5.3 times longer than chromosome 21.

I found information on human chromosome size from the statistics associated with the most recent version of the human genome (hg38).  I found a couple of diameters for human cheek cells on-line and took the middle value of 50 μm (microns...a millionth of a meter).

Chromosome 21 is 46,709,983 bp (base pairs) in length.  The length of a nucleotide incorporated in DNA is 0.34 nm (nanometers...a billionth of a meter).

Using Photoshop I made the cheek cell 1 inch wide (2.54 cm).  So if 50um = 1 inch then chromosome 21 would be 158.8 inches (403.5 cm).  I drew the line using Adobe Illustrator and kept adding to it until the total length was 158.8 inches.