Understanding the Chromosome Theory of Inheritance

The question asks about the scientists who proposed the chromosome theory of inheritance. This theory is a fundamental concept in genetics, linking the patterns of inheritance observed by Mendel to the behavior of chromosomes during meiosis.

What is the Chromosome Theory of Inheritance?

The chromosome theory of inheritance states that:

• Chromosomes are the structures that carry genetic information (genes).
• Genes are located at specific positions (loci) on chromosomes.
• Chromosomes undergo segregation and independent assortment during meiosis, which accounts for the segregation and independent assortment of genes observed by Mendel.
• Each parent contributes one set of chromosomes to their offspring through gametes (sperm and egg).

Proponents of the Chromosome Theory

The chromosome theory of inheritance was independently proposed by two scientists around the turn of the 20th century:

• Walter Sutton (in 1902) studied grasshopper chromosomes. He observed that chromosomes occur in pairs and that these pairs separate during meiosis. He recognized the parallel between the behavior of chromosomes and Mendel's laws of heredity.
• Theodor Boveri (around the same time, completing his work in 1902) studied sea urchin eggs. He showed that proper embryonic development requires a complete set of chromosomes. He also noted the consistent number of chromosomes in somatic cells and half that number in gametes, and how chromosomes behave during meiosis and fertilization.

Both Sutton and Boveri independently arrived at the conclusion that chromosomes are the carriers of hereditary units (genes).

Analyzing the Options

Let's look at the given options:

• Watson and Crick: James Watson and Francis Crick are famous for discovering the double helix structure of DNA in 1953. While their work is crucial to understanding genetics, they did not propose the chromosome theory of inheritance.
• Walter Sutton and Theodor Boveri: As discussed above, Walter Sutton and Theodor Boveri are credited with independently proposing the chromosome theory of inheritance, integrating Mendelian genetics with cytology.
• T. H. Morgan: Thomas Hunt Morgan, working with fruit flies (Drosophila melanogaster), provided strong experimental evidence that supported the chromosome theory of inheritance. His work on sex-linked inheritance and genetic linkage further solidified the idea that genes are located on chromosomes and can be mapped. However, he built upon the theory proposed by Sutton and Boveri; he was not the original proposer.
• More than one of the above: This would be true if multiple pairs/individuals listed proposed the theory, but only Sutton and Boveri are the primary proponents.
• None of the above: This is incorrect, as the theory was proposed by scientists listed in one of the options.

Based on the historical contributions to genetics, Walter Sutton and Theodor Boveri are the scientists credited with proposing the chromosome theory of inheritance.