The restriction enzymes that cut the bacteriophage dna cannot cut the bacterial chromosomal dna. explain this statement. the bacteria can cut the viral dna at its specific restriction site, but they cannot cut their own dna since bacterial chromosomal dna has altogether a different dna sequence than the viral dna. the bacteria can cut the viral dna at its specific restriction site but protect their own chromosomal dna by modifying its bases and blocking the restriction enzyme. the bacteria can cut the viral dna at its specific restriction site but protect their own chromosomal d

The correct answer is option (B)  The bacteria can cut the viral DNA at its specific restriction site but protect their own chromosomal DNA by modifying its bases and blocking the restriction enzyme.

Restriction enzymes cleave the double stranded DNA at specific points into fragments. Endonucleases cleave the internal or the non-terminal phosphodiester bonds after recognizing specific sequences on the DNA which are often palindromic. To prevent the destruction of its own DNA by the restriction enzymes, a few specific bases are modified in each strand by the addition of the methyl groups. Bacteria prevent their own DNA from being cut by the restriction enzyme through the methylation of the restriction sites. The process is called the restriction modification system found in the bacteria and other prokaryotic organisms.  

estuaries are the partially enclosed coastal bodies of brackish water formed at the mouth of sea where river meets an ocean. it is a transition zone between river and sea water so estuaries are influenced to both marine environment such as tides, waves and to riverine such as flow of fresh water and sediments. the mixing of sea and fresh water provide high level of nutrients, making estuaries a high product habitats.

many estuaries suffers degradation from a variety of human activities like erosion from deforestation, overgrazing, overfishing, drainage and eutrophication.

so from the above statement answers will be

1. false as estuaries are formed due to both brackish and freshwater.

2.true, due to high productivity estuaries are breeding ground for many marine species.

3. direct and indirect activities of man that contribute to pollution and deposition of sediments.