THE EXPERIMENT OF CURT STERN FOR CYTOLOGICAL BASIS OF CROSSING OVER

Curt Stern, a renowned geneticist, conducted an influential experiment to investigate the cytological basis of crossing over. His work significantly contributed to the understanding of genetic recombination and the mechanisms underlying it.

Background

Before delving into Stern’s experiment, it is important to understand the context in which it took place. The concept of crossing over, or genetic recombination, was first proposed by Thomas Hunt Morgan in 1911. He observed unexpected patterns of inheritance in his experiments with fruit flies, which led him to propose that exchange of genetic material occurs between homologous chromosomes during meiosis. This phenomenon was termed “crossing over,” and it laid the foundation for further research into the mechanisms of genetic recombination.

Objective of the Experiment

Stern’s experiment aimed to provide cytological evidence for the occurrence of crossing over during meiosis. He sought to observe and document physical manifestations of genetic recombination at the cellular level, using microscopy and cytological techniques.

Experimental Design

Stern utilized Drosophila melanogaster, commonly known as fruit flies, as his model organism for the experiment. Fruit flies have been instrumental in genetic research due to their short generation time, large number of offspring, and well-defined genetic traits.

Stern selected specific mutant strains of fruit flies that exhibited distinct phenotypic traits, such as eye color or wing morphology. By crossing these mutant strains, he created hybrid individuals with different combinations of these traits.

Observations and Analysis

Using microscopic analysis of the chromosomes in the hybrid individuals, Stern was able to observe physical evidence of crossing over. Specifically, he identified the presence of chromosomal configurations that could only be explained by recombination events occurring during meiosis.

By carefully documenting these cytological observations and correlating them with the inheritance patterns of specific traits in subsequent generations of fruit flies, Stern provided compelling evidence for the occurrence of crossing over and its role in generating genetic diversity.

Significance and Impact

Stern’s experiment had a profound impact on the understanding of genetic recombination. It provided direct cytological evidence for a process that was previously inferred from patterns of inheritance. His work contributed to the broader acceptance of the concept of crossing over and furthered our understanding of the mechanisms underlying genetic diversity and evolution.

In conclusion, Curt Stern’s experiment on the cytological basis of crossing over in Drosophila melanogaster significantly advanced our understanding of genetic recombination and its role in shaping genetic diversity.