Answer:
a. + glucose, + lactose = On
b. - glucose, - lactose = Off
c. + glucose, - lactose = Off
d. - glucose, + lactose = On
Explanation:
Lac operon has both types of control, repressible and inducible.
Whenever glucose level is low in the cell, an enzyme known as adenylyl cyclase raises the level of cAMP which forms a dimer with CRP protein and they both act as activator of lac operon and cause expression.
Apart from this, when lactose is present in the cell, β-galactosidase enzyme metabolizes lactose to form allolactose which causes allosteric repulsion in the lac repressor and causes its removal from the operator. As soon as repressor is removed lac operon gets activated.
In wild type lac operons, the expression of lac operon occurs when glucose level is low in the cell and lactose is present but in this mutant presence or absence of glucose will not make a difference because CRP will bind Plac promoter independent of cAMP level i.e. activator CRP will work even in high glucose concentration. If lactose is present then lac operon will always express so in option 'a & d' lac operon will express but in option 'b & c' it will not express.
Crop modification is when the DNA of a plant is altered, commonly used to make them more desirable. For example, bananas weren’t always these long and seedless fruits but with crop modification, over time scientists were able to change the DNA of the banana we know today.
Explanation:
Water splitting is the chemical reaction in which water is broken down into oxygen and hydrogen: 2 H2O → 2 H2 + O. Efficient and economical photochemical water splitting would be a technological breakthrough that could underpin a hydrogen economy.
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Answer: The quantity of water in the beaker will reduce. The cell will increase size.
Explanation: There is difference in water concentration between the cell and the beaker, therefore water will move from the beaker into the cell causing the cell to expand and the quantity of water in the beaker to decrease. There will be movement of water molecules from an area of high water concentration (beaker) to an area of low water concentration (the cell) through a selectively permeable cell membrane. The aim of this is to create an equilibrium between the water concentration in the cell and that in the beaker.
