Which scientist is credited with creating the first genetic map for maize and demonstrating recombination and the role of transposition in trait changes?

Which scientist is credited with creating the first genetic map for maize and demonstrating recombination and the role of transposition in trait changes?

• A. Mendel
• B. Darwin
• C. Watson
• D. McClintock

Answer: (D)

Barbara McClintock’s work in maize showed how genes are arranged on chromosomes and how they can move to new positions, causing trait changes. She built the first genetic map for maize by tracking recombination events, which reveal the relative order and distance between genes on a chromosome. At the same time, she discovered transposable elements—segments of DNA that can move within the genome—and demonstrated how their movement can alter gene function and lead to visible changes in kernels. This combination—mapping recombination and proving that genes can relocate via transposition—fits her work exactly. The other scientists listed contributed to genetics in different ways (Mendel founded inheritance, Darwin proposed natural selection, Watson and Crick described DNA’s structure) but did not demonstrate both maize genetic mapping and transposition in this way.

Barbara McClintock’s work in maize showed how genes are arranged on chromosomes and how they can move to new positions, causing trait changes. She built the first genetic map for maize by tracking recombination events, which reveal the relative order and distance between genes on a chromosome. At the same time, she discovered transposable elements—segments of DNA that can move within the genome—and demonstrated how their movement can alter gene function and lead to visible changes in kernels. This combination—mapping recombination and proving that genes can relocate via transposition—fits her work exactly. The other scientists listed contributed to genetics in different ways (Mendel founded inheritance, Darwin proposed natural selection, Watson and Crick described DNA’s structure) but did not demonstrate both maize genetic mapping and transposition in this way.