Barbara McClintock discovered that a controlling element was responsible for the mutant-spotted phenotype (purple spots on white) in corn kernels. Explain how this works
What will be an ideal response?
A normal C gene produces purple pigment in the corn kernel cells. If this gene is disrupted by the transposon Ds (a "mobile controlling element"), no pigment is produced, resulting in a white kernel. Reversions of this mutation can occur if Ds transposes out of the gene during development, resulting in spots of purple pigment on the kernel. The transposition of Ds is controlled by an autonomous "activator" element, Ac.
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The endodermis
(a) is the outer covering of the root. (b) is part of the vascular tissue. (c) contains the Casparian strip, which regulates the movement of substances. (d) is none of the above.
Distinguish between stromatolites and biosignatures
What will be an ideal response?
When considering time and temperature as factors in microbicidal activity,
A. time is not a factor, only temperature. B. they are inversely proportional to each other. C. they are directly proportional to each other. D. they must be of equal value e.g. 30 minutes at 30°C.
Auxin sprayed on tomato flowers stimulates the __________ to develop without the formation of
__________. a. roots; root hairs b. fruit; ovaries c. seeds; ovaries d. ovary; seeds e. seeds; fruits