Zusammenfassung der Ressource
Barbara McClintock
- Studied the hereditary characteristics of
corn and how these traits are passed down
through the generations and linked this to
changes in the plants’ chromosomes
- Proved the genetic elements can
sometimes change position on a
chromosome, which causes genes to
become active or inactive
- Discovered transposons
- Ac and Ds
- Additional experiments with the Ds locus
revealed that chromosome breakage at this
locus requires a second dominant
locus—the Ac locus
- The Ac locus can initiate its own transposition
- Ds chromosome breakage could be activated by an Ac
element that is at a different site or even on a different
chromosome
- Also found that insertion of Ac and Ds could lead to
unstable mutations, but moving those transposons
from the mutated loci could restore the gene’s function
- Found that depending on where they are inserted into a
chromosome, they can reversibly alter expression of
other genes
- During her time at Cornell, McClintock developed staining techniques in
order to visualize maize chromosomes
- Further refined these techniques to effectively discriminate between
each of the 10 maize chromosomes
- Also helped identify all of the maize linkage groups (genes that are
inherited together because of their proximity on the same chromosome)
- Demonstrated crossing-over at the
chromosomal level and showed that genetic
recombination involved the physical exchange
of chromosome segments (major contribution
to field of genetics)