Here are the 3 parts of the cell theory:
1. Cells are the basic building blocks of any living things.
2. Any living thing is composed of more than 2 cells.
3. New cella arise from the old
<span>The correct answer is d. the idea that T. rex held its tail aloft was supported by the studies of many scientists. This is how science works, things are discovered by having members of the scientific community do experiments and come to the same conclusion. Many of them confirmed this theory and a concensus was established.</span>
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.
D: Neutral mutation. It says the eyesight remains normal. Therefore it cannot be harmful. Changing eye color has no effect on the ability to find food. Eye color is just an appearance.
