In Escherichia coli (E. coli), the tryptophan operon encodes structural genes, including trpC, trpB, and trpA, that encode the tryptophan synthetase protein complex. A repressor protein encoded by the trpR gene regulates the trp operon. In the presence of high levels of tryptophan, tryptophan molecules bind the repressor protein and allow the repressor to recognize and bind to the operator, called trpO, and repress the expression of the structural tryptophan synthetase genes. In the absence of tryptophan, the repressor is unable to bind the operator and gene expression can occur. Assume any minus symbol represents a null mutant. What is the type of expression of each functional structural gene for the three bacterial strains?

Explanation:

in the absence of tryptophan, Trp operon expresses itself, and in the presence of tryptophan, repressor binds to the operator region and stop the expression of trp operon.

1- In trpR is mutated then the trp operon will be in the constitution expressed condition even in the presence of tryptophan amino acid.

for trpA - No expression as TrpA is mutated. So no expression

for trpB - constitutive

for trpC -constitutive

2- In this condition, Oc is mutated in such a way that repressor protein can no longer bind to it.

So

for trpA- constitutive.

for trpB - No expression as TrpB is mutated. So no expression.

for trpC - No expression TrpC is mutated. So no expression.

3- in this condition repressor from the merodiploid operon will express and in the presence of trp it will block the expression of trp operon.

for trpA- repressible.

for trpB - repressible.

for trpC - repressible.

question#1

ans:

cell is the basic unit of organization of all living things. cells are often called the building block of life and it is the smallest unit of life. the study of cell is called cell biology. cell consists of cytoplasm enclosed within membrane, which contain bio-molecules such as proteins and nucleic acid.

two third of cell is water, which means that two-third of your whole body is water. the rest is the mixture of molecules, mainly proteins, lipids and carbohydrates.

question#2

ans:

organ:

an organ is a group of tissues specialized to form a functional unit. an example is the heart in animals.

organ system:

an organ system is a group of several organs whose functions are synchronized to release an effective action in a living organism. an example is digestive system.

question#3

different systems perform different function at tissue level. for example, the respiratory system facilitates breathing. in the alveoli tissue of the lungs, the exchange of oxygen and carbon dioxide molecules between the air and the bloodstream occurs by passive transport, so that oxygen is taken in and carbon dioxide and water are removed. different systems of the body carry out different functions. for example, your digestive system is responsible for taking in and processing food, while your respiratory system working with your circulatory system is responsible for taking up oxygen and getting rid of carbon dioxide.

question#4

different systems perform different function at tissue level. for example, the respiratory system facilitates breathing. in the alveoli tissue of the lungs, the exchange of oxygen and carbon dioxide molecules between the air and the bloodstream occurs by passive transport, so that oxygen is taken in and carbon dioxide and water are removed. different systems of the body carry out different functions. for example, your digestive system is responsible for taking in and processing food, while your respiratory system—working with your circulatory system is responsible for taking up oxygen and getting rid of carbon dioxide.

question#5

our body works because of the interactions that happen between organs and organ systems.  

for example:  

the heart to regulate blood flow throughout the body. the blood carries oxygen and nutrients to the cells and carries carbon dioxide and waste away from the cells. body systems work together in maintaining a constant internal environment. when this balance is disrupted, the body systems may not function properly, and human health can suffer.   you start to feel bad.