The role of a metabolite that controls a repressible operon is toa) bind to the promoter region and decrease the affinity of rna polymerase for thepromoter. b) bind to the repressor protein and inactivate it. c) bind to the operator region and block the attachment of rna polymerase to the promoter. d) increase the production of inactive repressor proteins. e) bind to the repressor protein and activate it.

Ans. (E) bind to the repressor protein and activate it.

Repressible operon is defined as operon that normally remains active, but can be inhibit by a repressor molecule (a protein). When transcription of genes of a particular repressible operon is not required, a co-repressor( metabolite) molecule binds and activates the repressor molecule. The repressor protein, then binds to the operator and inhibits gene expression.

For example, tryptophan (tryp) operon is a repressible operon, responsible for the gene expression of enzymes for tryptophan synthesis. When tryptophan is present in sufficient amount, expression of tryp operon is not required.

The tryptophan (metabolite) itself, acts as co-repressor and activates repressor protein for tryp operon and inhibits expression of genes.

Thus, the correct answer is option (E).

d concave shape of wave rock

explanation:

the concave shape of wave rock is a very good evidence that supports the evolution of earth due to chemical weathering. if we talk about structure of   wave rock, studies have estimated that it is around 2.7 billion years old. it also serves as the foundation of evidence that it was the place where australian continent began to form.

how the structure of wave rock was created?

studies suggest that structure of wave rock was created when the surrounded area was started to weather due to which deposition of material started on the part of land which now contains wave rock.

the structure of wave rock is considered to be one of the best-known landforms in australia. at the height of around 15 cm, there can be found flared slopes which formulate the margins of hyden rock. it is now assumed by geologists that wave rock was created by subsurface water-induced weathering and not by glaciers, waves or wind.

due to deposition of material over the period of long time, the wave rock became tougher and tougher due to weathering from surrounding terrain. this makes it a physical evidence that supports   the evolution of earth due to chemical weathering.

hope it !

c) 50% there are four chromosomes. after crossing over, 2 of the four have been changed. that means any gamete has a 2 in 4 chance or 50% chance of receiving the mutated chromosome.