Rats carry bacteria that cause bubonic plaque. Fleas that bite the rats

1 answer:

6 0

B- Parasite.

The fleas survive by ingesting the blood of warm-blooded animals.
The bacteria survive inside or on another organisms.

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For this assignment you will complete an illustration(s) (by hand) of how the lac operon works. You should be sure to include de

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<h2>Lac operon </h2>

Explanation:

Lac operon present in prokaryotic chromosomes whose product involves in transportation and catabolism of lactose

Lac operon consists of three structural genes called Lac Z,Lac Y and Lac A and a regulatory element(promoter and operator)
Lac I gene is present outside the Lac operon,act as regulatory gene and control the expression of Lac operon genes
Lac Z codes for β galactosidase which converts lactose into allolactose
Lac Y codes for Lac permease which act as a membrane transporter and transport lactose into the cells
Lac A codes for transacetylase which neutralize the toxic effects of lactose

Lac operon in absence of lactose

In absence of lactose Lac operon exists in switch off state
Lac I gene produces Lac repressor which binds to operator region and prevent binding of RNA Polymerase thus blocks transcription

Lac operon in presence of lactose

In presence of lactose Lac operon exists in switch on state
In presence of lactose few molecules of Lac operon enzyme catalyse conversion of lactose to allolactose
Allolactose act as an inducer,binds to the Lac repressor and induce conformational changes causing dissociation of Lac repressor from operator
In absence of Lac repressor RNA Polymerase binds to the promoter and starts transcription of genes which catabolize lactose

Lac promoter is a weak promoter and direct transcription of Lac operon genes in very low level in presence of lactose

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CAP cAMP complex binds to the upstream of promoter called CAP binding site and stimulate expression of Lac operon genes by facilitating binding of RNA Polymerase
Catabolite activator protein(CAP) or cAMP receptor protein(CRP) activate when cAMP binds
cAMP is a secondary messenger synthesized from ATP and act as co-activator of CRP
With respect to CAP cAMP complex Lac operon system is positively controlled
In prokaryotic cell cAMP is very low when glucose concentration is relatively high and vice versa
At high concentration of glucose the growth rate is maximum and lactose catabolism is repressed called catabolite repression

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