Read the following paragraph carefully and answer the given questions. In the year 1963 the two enzymes responsible for restricting the growth of bacteriophage in E. coli were isolated. The first restriction endonuclease - Hind II, whose functioning depended on a specific DNA nucleotide sequence was characterized five years later. It was found that Hind II always cut DNA molecules at a particular point by recognizing a specific sequence of six base pairs. This specific base sequence is known as the recognition sequence for Hind II. Besides Hind II, today we know more than 900 restriction enzymes that have been isolated from over 230 strains of bacteria, each of which recognize different recognition sequences. |
Hind II is a restriction endonuclease because - |
It removes nucleotides from the ends of DNA. It makes cut at specific positions within the DNA. It recognizes palindromic RNA sequences. It can join any two DNA sequences at specific points. |
It makes cut at specific positions within the DNA. |
The correct answer is Option (2) → It makes cut at specific positions within the DNA. Restriction Endonucleases (Molecular Scissors): Restriction enzymes belong to a larger class of enzymes called nucleases. These are enzymes that are commonly referred to as "molecular scissors" because they cut DNA molecules at specific recognition sequences. These recognition sequences are often palindromic, meaning the sequence reads the same forwards and backward. Restriction enzymes belong to a larger class of enzymes called nucleases. These are of two kinds; exonucleases and endonucleases. Exonucleases remove nucleotides from the ends of the DNA whereas, endonucleases make cuts at specific positions within the DNA. The first restriction endonuclease–Hind II, whose functioning depended on a specific DNA nucleotide sequence was isolated and characterized five years later. It was found that Hind II always cut DNA molecules at a particular point by recognizing a specific sequence of six base pairs. This specific base sequence is known as the recognition sequence for Hind II. |