Genetic engineering is possible because of special enzymes that cut DNA. These enzymes are called restriction enzymes or restriction endonucleases. Restriction enzymes are proteins produced by bacteria to prevent or restrict invasion by foreign DNA. They act as DNA scissors, cutting the foreign DNA into pieces so that it cannot function. These enzymes are routinely used for DNA modification in laboratories and are a vital tool in molecular cloning.

Prokaryotic (bacterial) flagella is 3 to 12 μm long, 0.01 to 0.02 μm thick hollow unistranded and made of 3 to 8 spiral or helically arranged rows of protein, flagellin.

Smooth muscles are plain, non-striated, involuntary, or unstriped muscles due to the absence of striations. These muscles occur in the walls of hollow internal organs, in capsules of lymph glands, spleen, etc., in iris and ciliary body of eyes, skin dermis, penis, and other accessory genitalia, etc.

Aromatic amino acids, like other proteinogenic amino acids, are the building blocks of proteins and include phenylalanine, tryptophan, and tyrosine. All plants and micro-organisms synthesize their own aromatic amino acids to make proteins 

Tyrosine is the only one of the aromatic amino acids with an ionizable side chain. Tyrosine is one of three hydroxyl-containing amino acids

Suspended particles is removed by primary treatment.

Primary Treatment:

• All the solid particulate matter are removed by primary treatment.
• Floating debris is removed by sequential filtration.
• The grit (soil and small pebbles) are removed by sedimentation.
• The solids settle as primary sludge and the supernatant as effluent.
• The effluent moves from primary settling tank to large aeration tanks for secondary treatment.​

Epidermophyton is a genus of fungi. This fungi causes ringworm infections. This belongs to Ascomycetes. This is known to cause infections of skin and nails. Mucor is a common mould. It is filamentous fungi found on decaying fruits and vegetables. Thus both belong to same kingdom i.e. Kingdom Fungi.

To test for chlorine, use damp blue litmus paper. The blue colour will turn red and then to white. Chlorine gas reacts with water to produce an acidic solution which is also an effective bleach. This explains how the test for chlorine works. The acidic solution formed on the damp litmus paper turns the indicator red. Then the bleach turns the red colour to white.