You are working with a chromosome that it 10 7 base pairs long, and want to cut
ID: 58990 • Letter: Y
Question
You are working with a chromosome that it 107 base pairs long, and want to cut it into blunt-ended fragments in the range of 103-104 base pairs. Which restriction endonuclease would you choose from the list below? (Note that “^” indicates the site of cleavage)
PmeI (GTTT^AAAC)
BamHI (G^GATCC)
EcoRV (GAT^ATC)
BstUI (CG^CG)
BstKTI (GAT^C)
I thought the answer was C, because EcoRV is used as a restriction enzyme. EcoRV creates blunt ends when it cuts, so I now know this cannot be the answer because I want to actually cut into the blunt ends, not create them. I know the answer is Pmel because Pmel cuts leaves 4 base pairs on the 3’ end.
How many EcoRI sites are there in the plasmid?
0
1
2
3
Cannot be determined
I know the first answer is pmel. But I don't know how many ECORI are there. could someone help me and tell me why it is that many?
Explanation / Answer
The probability of presence of PmeI restriction site is for every 48 = 65536 base pairs.
Therefore, the number of PmeI restriction sites in 107 base pairs long sequence = 152.58
The probability of presence of BamHI restriction site is for every 46 = 4096 base pairs.
Therefore, the number of BamH restriction sites in 107 base pairs long sequence = 2441.406
The probability of presence of EcoRV restriction site is for every 46 = 4096 base pairs.
Therefore, the number of EcoRV restriction sites in 107 base pairs long sequence = 2441.406
The probability of presence of BstUI restriction site is for every 44 = 256 base pairs.
Therefore, the number of BstUI restriction sites in 107 base pairs long sequence = 39062.5
The probability of presence of BstKTI restriction site is for every 44 = 256 base pairs.
Therefore, the number of BstKTI restriction sites in 107 base pairs long sequence = 39062.5
Thus, there are 2441.406 EcoRV restriction sites.
We can use either EcoRV or BstUI to get blunt ends in the range of 103 to 104 base pairs.