Noble laureate Barbara McClintock observed frequent breakage of maize chromosome 9 due to which of the following transposons ?
MH SET - 2021, SET Exam - 2021,
Answer: B
McClintock's chromosome 9 breakage was due to Ac-Ds (Activator-Dissociator elements).
Working on maize in the 1940s, Barbara McClintock found a site on the short arm of chromosome 9 where the chromosome broke repeatedly, giving variegated kernels. She called the element at that site Dissociation (Ds) and showed that its breaks and movements depended on a second element, Activator (Ac), which supplies the transposase. Ds is a defective element that cannot move alone. This work earned her the Nobel Prize in 1983.
IS elements are bacterial, Mutator was found in maize later by others, and Spm/En, which McClintock also studied, is a separate family not tied to this breakage.
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