he answer is because <span>samples of air taken over erupting volcanoes shows that volcanoes
contribute a small amount of chlorine in the stratosphere compared to CFCs. Volcanic
eruptions account for a large instability of chlorine from land to the
atmosphere on a yearly basis. This is in addition to chlorine that enters the
atmosphere from sea spray, industrial processes and biological gases which are
from CFCs. All of these inputs happen near or at the base of the atmosphere. Very
little of the material emitted from volcanoes makes it up into the upper
reaches of our atmosphere which is the stratosphere where it could touch the
ozone layer. However, most of it is believed to be deposited lower down which
is in the troposphere, where it then rained out back to the surface of the
earth.</span>
negative- Thermoregulation (if body temperature changes, mechanisms are induced to restore normal levels) Blood sugar regulation (insulin lowers blood glucose when levels are high ; glucagon raises blood glucose when levels are low)
positive- contractions in child birth and the ripening of fruit; negative feedback examples include the regulation of blood glucose levels and osmoregulation.
(i got this from google btw)
hope this helped :) pls give brainiest
Explanation:
I think the answer is B hopefully it's right
Answer:
a regulatory protein binds to DNA which blocks transcription
Explanation:
Negative control of gene expression includes the binding of certain regulatory proteins to the regulatory sequences. This binding prevents the expression of certain sets of the gene. For instance, binding of repressor protein to the operator sequence of lac operon prevents the expression of structural genes of the operon. This pattern of gene regulation is called negative regulation. The binding of the repressor to the operator sequence does not allow the RNA polymerase to transcribe genes since the operator and promoter (binding site for RNA polymerase) sequences are present in close vicinity.