Do eukaryotic cells have restriction endonucleases? Justify your answer.
No, eukaryotic cells do not have restriction endonucleases.
Restriction endonucleases are enzymes that make cuts at specific positions within the DNA by recognising specific palindromic nucleotide sequences. According to the provided text, these enzymes have been isolated from over 230 strains of bacteria.
The naming convention for restriction enzymes clearly indicates their source – the first letter comes from the genus and the second two letters come from the species of the prokaryotic cell from which they were isolated. For example, EcoRI comes from Escherichia coli RY 13, which is a bacterium (prokaryote). The text does not mention any eukaryotic source for restriction endonucleases, indicating they are found only in prokaryotic cells (bacteria).
Explanation
The textbook context explicitly states that restriction enzymes are isolated from bacteria (prokaryotic cells). The naming convention section specifically uses the phrase 'prokaryotic cell from which they were isolated', and all examples given (Hind II, EcoRI) are from bacterial sources. This clearly establishes that restriction endonucleases are prokaryotic enzymes, not found in eukaryotic cells.
Solution Steps
Step 1: Identify the source of restriction endonucleases from the text - 'isolated from over 230 strains of bacteria'
Step 2: Note the naming convention reference to 'prokaryotic cell'
Step 3: Conclude that since restriction endonucleases are prokaryotic in origin, eukaryotic cells do not have them