Chromosome Theory of Heredity Explained


The Chromosome Theory of Heredity was one of the fundamental theories of genetics that helped to unify the idea that there were ties that binds humanity together. Proposed by Walter Sutton and Theodore Boveri, who were working independently of each other, this is the first theory which identified the chromosome as the carrier of genetic materials.

This theory also explains the mechanisms of Mendelian inheritance correctly. It was the first theory to identify chromosomes which would have paired factors and linear structures at specific sites within the human body.

It is common to refer to this theory as the Chromosome Theory of Inheritance.

What Are the 5 Key Points of the Chromosome Theory of Heredity

When Sutton first published his work on the theory of heredity in 1902, there were 5 key points that were being developed to support the arguments of the idea. In 1903, Boveri published papers which proposed essentially the same thing, though his work was focused on the study of sea urchins, while Sutton was studying grasshoppers.

This led to the development of 5 key points that are expressed within the Chromosome Theory of Heredity.

1. Chromosome groups of presynaptic cells are made up of two equivalent series of chromosomes. Strong ground exists for the conclusion that one chromosome is contributed maternally and the other is contributed paternally.

2. A process referred to as pseudo-reduction allows for the pairing of homologous members so that the individually contributed chromosomes can be unionized.

3. Maturation mitosis, or the first post-synaptic, is equational. This means the result from the process is a lack of differentiation within the chromosomes.

4. A second post-synaptic division occurs, which is a reducing action. This results in the separation of the chromosomes that have conjugated in synapsis, which relegates them to different cells.

5. Chromosomes retain a level of morphing individuality throughout the various cell divisions which occur in a living being.

These ideas of linked heritage would be combined into the theory of heredity with the work of E.B. Wilson, who would publish a textbook on modern biology called “The Cell.” Wilson was friends with Boveri, but Sutton was his student. This led him to include the theory in his publication as the “Sutton-Boveri Theory.”

The name preference may be reversed today, but the theory remains the same.

What About the Work of Thomas Morgan?

Thomas Morgan was also quite fascinated with the idea of heredity playing a role in biology. Some even refer to Morgan as one of the founding fathers of modern genetics. He would win the Nobel Prize in Physiology or Medicine in 1933 for his work that helped to confirm that chromosomes play a role in heredity.

Boveri may have worked with sea urchins and Sutton may have worked with grasshoppers, but Morgan preferred to work with fruit flies. Regular fruit flies have red eyes. Morgan mated a red-eyed female fruit fly to a white-eyes male fruit fly and discovered all the offspring would have red eyes. Because red eyes are dominant, this was an expected result because of the patterns of dominant and recessive inheritance.

When Morgan made a reciprocal cross, however, he discovered that all the male fruit flies had white eyes, but all the female fruit flies had red eyes. To Morgan, this initial result seemed to violate the rule of independent assortment. The only way to explain the results, in fact, was if there was a genetic factor that caused eye coloration on an X chromosome.

By discovering this trait of genetics, Morgan would go on to help support the Chromosome Theory of Heredity. Although his work wasn’t the first to propose the idea, it was critical in confirming the observations and proposals made by Sutton and Boveri about 20 years before his work was published.

What Is the Implications for Humanity?

Humans follows a similar pattern of gene linkage. This means there is genetic information available on each chromosome. Yet no matter how they line up together, the only possibilities that may occur are based on the parental types that are available.

This means we can predict certain offspring outcomes through pedigree analysis. We can determine if there are autosomal recessive traits, autosomal dominant traits, or X-linked / Y-linked recessive traits by looking at the genetics of each parent.

In dominant scenarios, only one parent carries an allele. In recessive scenarios, both parents must carry an allele. Then, in linked recessive traits, the outcome will only affect a specific gender.

By understanding how genetic information is passed along, it becomes possible to know what to expect for the health of any offspring. This is all due to the Chromosome Theory of Heredity.