Thomas Hunt Morgan

Definition

Thomas Hunt Morgan was a pioneering American geneticist who played a crucial role in the early 20th century in establishing the field of genetics through his work with fruit flies (Drosophila melanogaster). He demonstrated that genes are located on chromosomes and developed the concept of linkage and crossing over, which laid the foundation for understanding heredity and gene mapping.

5 Must Know Facts For Your Next Test

1. Morgan's work with Drosophila led to the discovery of sex-linked traits, most famously the white-eye mutation, which provided evidence for the chromosomal basis of inheritance.
2. He introduced the concept of gene mapping, using three-point crosses to determine the order of genes on a chromosome and the distances between them.
3. Morgan won the Nobel Prize in Physiology or Medicine in 1933 for his discoveries related to heredity and genetic linkage.
4. His laboratory at Columbia University became a center for genetic research, producing numerous influential geneticists who furthered the field.
5. Morgan's research helped shift the focus in genetics from Mendelian inheritance to a chromosomal basis, fundamentally changing how scientists understood genetic transmission.

Review Questions

• How did Thomas Hunt Morgan's experiments with Drosophila melanogaster contribute to our understanding of linkage and gene mapping?
  • Morgan's experiments with Drosophila melanogaster demonstrated that certain traits were linked to specific chromosomes. By conducting crosses and analyzing the offspring, he showed that genes located close to each other on the same chromosome tend to be inherited together, establishing the concept of linkage. Additionally, his development of three-point crosses allowed researchers to map genes based on their recombination frequencies, providing a method to determine gene order and distance on chromosomes.
• Discuss the implications of Morgan's findings on the concept of crossing over in relation to genetic variation and heredity.
  • Morgan's findings on crossing over highlighted its role in increasing genetic variation among offspring. During meiosis, crossing over occurs when homologous chromosomes exchange segments, leading to new combinations of alleles. This process not only contributes to genetic diversity but also provided insight into how traits could be inherited independently despite being located on the same chromosome. His work reinforced the importance of understanding both linkage and crossing over in predicting inheritance patterns.
• Evaluate how Thomas Hunt Morgan's contributions transformed genetics from Mendelian inheritance to a more comprehensive understanding based on chromosomal behavior.
  • Thomas Hunt Morgan's contributions marked a significant shift from solely Mendelian genetics to a broader understanding that incorporated chromosomal behavior. By establishing that genes are located on chromosomes and demonstrating how linkage and crossing over affect inheritance patterns, he provided a mechanistic framework for heredity. This transformation allowed future generations of scientists to explore more complex genetic phenomena, such as polygenic inheritance and genomic mapping, ultimately shaping modern genetics as we know it today.

Related terms

Drosophila melanogaster: A small fruit fly widely used as a model organism in genetic research due to its short life cycle and the ease of observing genetic traits.

Linkage: The tendency of genes located close to each other on the same chromosome to be inherited together during meiosis.

Crossing Over: The process during meiosis where homologous chromosomes exchange genetic material, leading to genetic variation in offspring.