**Number of 6 amino purines present in 18 palindromes recognized by EcoR 1 restriction enzymes**

To determine the number of 6 amino purines present in 18 palindromes recognized by the EcoR 1 restriction enzyme, we need to first understand the recognition sequence of EcoR 1 and the structure of palindromes.

**EcoR 1 Recognition Sequence:**
The EcoR 1 restriction enzyme recognizes a specific sequence of DNA known as a recognition sequence. The recognition sequence for EcoR 1 is 5'-GAATTC-3' (where the hyphen represents the phosphodiester bond between nucleotides).

**Structure of Palindromes:**
A palindrome is a sequence of DNA that reads the same on both strands when read in the 5' to 3' direction. In other words, the sequence on one strand is the reverse complement of the sequence on the other strand.

**Analysis:**
1. The recognition sequence for EcoR 1 is 5'-GAATTC-3'.
2. Since the recognition sequence is palindromic, the complementary strand will also have the same sequence in the opposite orientation (3'-CTTAAG-5').
3. For each palindrome recognized by EcoR 1, there will be two recognition sequences present, one on each strand.
4. The number of 6 amino purines (adenine and guanine) present in each recognition sequence is 2, as there are two adenine (A) bases and two guanine (G) bases in the sequence.
5. Therefore, the total number of 6 amino purines present in each palindrome is 2 + 2 = 4.
6. Since there are 18 palindromes recognized by EcoR 1, we can calculate the total number of 6 amino purines by multiplying the number of palindromes (18) by the number of 6 amino purines per palindrome (4).
7. 18 x 4 = 72.

**Answer:**
Therefore, the correct answer is 72, option 2. There are 72 6 amino purines present in the 18 palindromes recognized by the EcoR 1 restriction enzymes.