79. The restriction site for Van91I is 5′ CCANNNN↓NTGG 3′. How many times can Van91I cut a 4 Mb bacterial
genome with 50% GC content?
1. 1000 times
2. 10 times
3. Once
4. 100 times

Detailed Explanation:

The Van91I restriction enzyme recognizes a specific sequence (5′ CCANNNN↓NTGG 3′) and cuts DNA at this site. To calculate how many times Van91I will cut a 4 Mb bacterial genome, you need to consider the probability of the restriction site occurring based on the sequence composition. With 50% GC content, there is a 1 in 4 chance of finding each base pair (A, T, C, G). The enzyme will cut roughly 1000 times in the genome.

Thus, the correct answer is:
1. 1000 times