Linkage and Gene Maps

T. H. MorganLexington Native

UK AlumniNobel Prize Winne

Thomas Hunt Morgan

• Lexingtonian Thomas Hunt Morgan worked on the fruit fly, Drosophila melanogaster.

• Morgan showed that Mendel’s principles applied to animals and not just pea plants.

• He was the first Kentuckian (and only… for now) to be awarded the Nobel Prize in Medicine.

• He was awarded this for determining that some traits were sex-linked and found on sex chromosomes. We’ll discuss this more later

T. H. Morgan

• He also discovered the principle of linkage.

• He discovered that each chromosomes is a set of linked genes.

• He found that chromosomes assort independently, not individual genes.

Crossing Over and Gene Maps

• Crossing over occasionally separates linked genes and produces new combinations of alleles.

• This is important for genetic diversity.

Alfred Sturtevant

• Alfred Sturtevant, a student in Morgan’s lab found that the further two genes are apart, the less likely they are to be inherited together.

Gene Maps

• Sturtevant created a gene map, which shows the relative location of genes on a chromosome.

• The map units are now called centimorgans (cM) in honor of T. H. Morgan

Crossing Over, Mutations, and Genetic Diversity

• Very rare genetic mutation, a yellow Northern Carindal