Question

what is SPM what is its components from no google first ans will brainliest ans for 54 points

Answer 1

The Suppressor-mutator control system
is so called because its regulator element,
also designated Spm, has two components
of action. The suppressor (or inhibitor)
component, component-l, directly regu-
lates the expression of a gene that has
come under the control of the Spm
system. Such control, it will be remembered, arises through insertion of the
operator element of the system at the
locus of a gene. When component-l of
Spm is in an active phase, the expression
of the gene is suppressed; when it is
inactive, gene action is expressed. One
exception to this general rule concerns the
modified gene locus uIm-?. This gene is
active when component-l is active, and
suppressed when it. is inactive. Com-
ponent-2 of Spm is the mutator or trans-
position-inducing component. The re-
sponse of the operator element to
component-2 often gives rise to a mutant
expression of the gene that releases it
from control by the Spm system. Some
responses, on the other hand, effect other
modifications that are not associated
with release but instead alter the sub-
sequent types of response of the operator
element to the components of Spm.
These modifications have been called
“changes in state” of the gene locus.
With some altered states, the operator
element loses its capacity to respond to
component-2, although it retains its abil-
ity to respond to component-l. No further
mutations occur, nor is the gene released
from control by the system. Its action
remains permanently under the control
of component-l of the Spm regulator
element.
Both components of Spm may undergo
change. Component-l exhibits alternat-
inp: cvcles of activitv and inactivity
whose regulation has been outlined in
previous reports. Changes of component-2
resemble mutations in that they arise
from single events, each of which alters
the effectiveness of this component, both
for inducing responses of the operator
element that lead to changes in gene
expression, and for inducing trans-
positions of Spm. Such alterations in
action of component-2 have been detected
only in those cells of the plant in which
component-l is active. Some alterations
eliminate all activity of component-2
whereas others effect altered times and
frequencies of occurrence of mutation-
inducing responses of the operator ele-
ment. Each mutant of component-2 may
undergo still further mutation, the fre-
quency of occurrence differing with
different mutants.
The components of Spm and their
characteristic modes of action were
detected originally in observations of the
activity of one gene that is under the
control of the Spm system. Although it is
possible to distinguish a change in action
of either component through such obser-
vations, distinctions are greatly facili-
tated when two or more genes, each under
the control of the system, are present in
a plant or kernel. The operator elements
at the different gene loci respond in like
manner to modificat’ions affecting either
of the components. Through such combi-
nations it has been possible to determine
with a considerable degree of accuracy the
types of modification undergone by each
of the components of Spm.
mark me as brainiest
bcoz this is not from Google
it is from a book