Thomas Hunt Morgan was an American evolutionary biologist, geneticist, embryologist, and science author who won the Nobel Prize in Physiology or Medicine in 1933 for discoveries elucidating the role that the chromosome plays in heredity.
Morgan in 1891
In a typical Drosophila genetics experiment, male and female flies with known phenotypes are put in a jar to mate; females must be virgins. Eggs are laid in porridge which the larvae feed on; when the life cycle is complete, the progeny are scored for the inheritance of the trait of interest.
Morgan's illustration of crossing over, from his 1916 A Critique of the Theory of Evolution
A chromosome is a package of DNA with part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells the most important of these proteins are the histones. These proteins, aided by chaperone proteins, bind to and condense the DNA molecule to maintain its integrity. These chromosomes display a complex three-dimensional structure, which plays a significant role in transcriptional regulation.
Human chromosomes during metaphase
The 23 human chromosome territories during prometaphase in fibroblast cells
Image: Theodor Boveri
