The frequency of recombination between gene pairs on the same chromosome on the same chromosome as a measure of the distance between genes was explained by?

• A. T.M. Morgan
• B. Gregor J. Mendel
• C. Alfred Sturtevant
• D. Sutton Boveri

The frequency of recombination between gene pairs on the same chromosome as a measure of the distance between genes was explained by C. Alfred Sturtevant. Sturtevant was a student of Thomas Hunt Morgan and is credited with creating the first genetic map based on recombination frequencies. Let’s delve deeper into how this concept works and why Sturtevant's contributions were pivotal in genetics.

The Basics of Genetic Mapping

To understand the significance of recombination frequency, we first need to grasp what recombination is. Recombination occurs during meiosis, the process of cell division that produces gametes (sperm and eggs). During this process, homologous chromosomes exchange segments of DNA, leading to new combinations of alleles. This exchange can result in offspring that have different traits from their parents.

Recombination Frequency as a Measure of Distance

The key idea here is that the frequency of recombination between two genes can indicate how far apart they are on a chromosome. If two genes are located close to each other, they are less likely to be separated during recombination. Conversely, if they are far apart, the likelihood of recombination occurring between them increases.

• Close Genes: Low recombination frequency (e.g., 1% means they are 1 map unit apart).
• Far Apart Genes: High recombination frequency (e.g., 50% means they are on different chromosomes or very far apart).

Sturtevant's Contribution

Alfred Sturtevant took the foundational work of his mentor, T.H. Morgan, and applied it to create the first genetic map. He used the recombination frequencies he observed in fruit flies (Drosophila melanogaster) to estimate the relative positions of genes on chromosomes. By calculating the percentage of offspring that exhibited recombination, he could infer the distances between genes.

Creating the Genetic Map

Sturtevant's method involved the following logical steps:

1. Cross two organisms with known traits to produce offspring.
2. Count the number of offspring exhibiting parental versus recombinant traits.
3. Calculate the recombination frequency using the formula:

Recombination Frequency (%) = (Number of Recombinant Offspring / Total Offspring) x 100

By applying this formula, Sturtevant could create a map that visually represented the arrangement of genes on a chromosome, allowing scientists to understand genetic linkage and inheritance patterns better.

Implications of Sturtevant's Work

The implications of Sturtevant's genetic mapping were profound. It laid the groundwork for modern genetics, enabling researchers to identify genes associated with diseases, understand evolutionary relationships, and even manipulate genetic material in biotechnology. His work demonstrated that genes are not randomly distributed but are organized in a specific manner along chromosomes.

In summary, Alfred Sturtevant's pioneering work in using recombination frequency to measure gene distance fundamentally changed our understanding of genetics and heredity. His contributions continue to influence genetic research and applications today.