Question

1. How do bacteria protect their own DNA from their restriction enzymes?

2. In case of amount of DNA fragments when are the following DNA cloning vectors are used: a. Bacterial plasmids , b. Bacteriophages,cosmids, and yeast artificial chromosomes (YAC)

3. Restriction enzymes cut DNA at specific sequences known as _________.

Answer 1

1. Bacteria protect their own DNA from their restriction enzymes by methylation. As bacterial DNA is methylated at certain regions, it cannot be recognized by the restriction enzymes.
2. The length of the DNA fragment that can be inserted into the vector: Plasmid - up to 15 kb, bacteriophage - 35 - 50 kb, cosmid - 30 - 45 kb, YAC - 90 - 300 kb.
3. Restriction sites.